This isn't a great way of thinking about intangible value, since most people are far less liquid than the value of the things in their lives. If your mom needs life-saving treatment for $10,000 and you can't afford to pay it, does that mean your mom is really worth less than $10,000 to you? No - her existence might contribute hundreds of thousands of dollars of devotion, emotional support, and sage advice to you. It's just that nobody will accept those things as collateral for a loan.
The Colosseum doesn't have as stark a value proposition going for it, but by a similar argument it's easy to imagine the public benefit of some building being greater than the amount of money that can be raised to support it. Personally, I think the Colosseum is mostly only valuable to the Italian state for the legitimacy that it buys it, a little self-justifying scheme of wasting taxpayer money to manufacture taxpayer assent.
I disagree about the transfer costs making Harberger tax unworkable, that gets priced into the self-assessed property value. You pay taxes on the use value of the property to you, not the market value, which is typically lower. When you want to sell, you'll offer at the lower market rate.
But this actually points to an even larger problem. Harberger taxes as such would be incredibly destructive to communities. The stronger the community, the higher the use value, meaning the higher the self-assessed tax rate would have to be in order to reflect the worth to you. But the value from community is uncashable, meaning that there's an unjust tax burden for having a better community. And people are usually only liquid to a minute proportion of the value of the intangible things in their lives.
Thus, people likely have to assess below their use value, which means the community can be eroded by compulsory sale and eviction. This already occurs in rent-paying communities, which are destroyed when property value goes up and they can no longer afford to rent there.
Tbh, you probably end up fighting this by having your neighbors in the community firebomb the property which got bought out from under you.
I think you can just drop the 'zero notice' part, add something like a 90 day delay between sale and transfer, and things would be a lot more workable.
There's another problem that your comment makes me think of - in a lot of cases, the easiest and most profitable thing to do will be to just buy the property and offer to lease it back to the previous owner at a higher rate than they were last paying in Harberger tax. With capital accumulation, you'll probably end up with giant extractive leasing company monopolies practically owning unwilling renters with no outside options - not sure what to do about this.
If anything, it'll be more common for the previous owner to trash the place on their way out with some excuse for avoiding legal damages.
I think in the typical Harberger scheme, in order to compel transfer of property rights, you pay the entire capital cost of the property, not some portion as a temporary rent.
My proposed solution to both your problem and Richard's, explained further in a separate comment, is that payment and transfer be separated by enough time to vacate amicably, or sue to enjoin transfer.
where the value to an actor of some property might be less than the amount of value they have custody over via that property.
I don't think those are separate things? The value of a roof is the value of everything underneath it when it rains.
Property owners are only going to assess their property for tax purposes at perceived market value if they're ready to sell. Otherwise they'll assess it higher, factoring in moving costs. The Harberger buyer is usually overpaying.
For this reason, I think most Harberger extortion is easily avoidable by adding a sufficient delay between sale time and transfer time. For example, for most categories of residential and commercial real estate, a reasonable expectation for compulsory sale would be perhaps 90 days between purchase and transfer. (This is already the custom for foreclosures, I think.) The compelled seller, having priced in moving costs, will have time to decide how to put their new liquidity to use and make the proper adjustments or sue to enjoin the transfer if maliciousness such as repeat harassment is suspected.
This leaves the problem of sudden price changes. One solution is to make compulsory sales begin as blind auctions. If someone submits a blind bid for your property at or above your self-assessed tax value, you get a short period of time to submit a reassessment, and if your bid is higher you pay back taxes on that reassessment within that tax year, otherwise they buy from you at their assessment. I think this scheme gets both bidders to bid their true rates, and discourages holdouts approximately the same amount? It makes the market slightly less efficient but keeps the same tax efficiency.
You correctly imply something worth restating clearly: despite their initial framing, impact markets are not a way to achieve public goods per se, they are a way to efficiently achieve funder goals in contexts where the path to that goal is uncertain, there are many plausible options, and there is lots of information that can be potentially priced into the market about those options.
With some impact market designs decentralized self interest can in fact come into play, perhaps in the form of bounty pools pledged into escrow by some subset of the people who would benefit from the existence of the public good they are offering the bounty for. In this case funders have a vested interest in what is achieved, and will evaluate based on such. Maybe in the long run markets that enable such a design will gain reputability relative to markets solely funded and assessed by fly-by philanthropists.
I agree with you that disinterested funders often end up having counterproductive goals, although not in all domains. The above example of generic pharmaceutical repurposing trials might be such, where the market can bear useful information about which of many interventions would have the highest impact and chance of success, but the work to achieve that goal is kind of hard to do serious harm with, given that the risk profiles of those drugs is already well quantified. In such cases I see especially little risk to encouraging philanthropy.
If some funder intentionally wishes to achieve nefarious goals with impact markets, I admit the existence of impact market infrastructure might facilitate that. But we have legal and social tools to counteract bad ends and I don’t think that impact markets are so powerful as to enable an end run around these.
Even granting that there are grabby aliens in your cosmic neighborhood (click here to chat with them*), I find the case for SETI-risk entirely unpersuasive (as in, trillionths of a percent plausible, or indistinguishable from cosmic background uncertainty), and will summarize some of the arguments others have already made against it and some of my own. I think it is so implausible that I don't see any need to urge SETI to change their policy. [Throwing in a bunch of completely spitballed, mostly-meaningless felt-sense order-of-magnitude probability estimates.]
Parsability. As Ben points out, conveying meaning is hard. Language is highly arbitrary; the aliens are going to know enough about human languages to have a crack at composing bytestrings that compile executable code? No chance if undirected transmission, 1% if directed transmission intended to exploit my civilization in particular.
System complexity. Dweomite is correct that conveying meaning to computers is even harder. There is far too much flexibility, and far too many arbitrary and idiosyncratic choices made in computer architectures and programming languages. No chance if undirected, 10% if directed, conditioning on all above conditions being fulfilled.
Transmission fidelity. If you want to transmit encrypted messages or program code, you can't be dropping bits. Do you know what frequency I'm listening on, and what my sample depth is? The orbital period of my planet and the location of my telescope? What the interplanetary and terrestrial weather conditions that day are going to be, you being presumably light-years away or you'd have chosen a different attack vector? You want to mail me a bomb, but you're shipping it in parts, expecting all the pieces to get there, and asking me to build it myself as well? 0.01% chance if undirected, 1% if directed, conditioning on all above conditions being fulfilled.
Compute. As MichaelStJules's comment suggests, if the compute needed to reproduce powerful AI is anything like Ajeya's estimates, who cares if some random asshole runs the thing on their PC? No chance if undirected, 1% if directed, conditioning on all above conditions being fulfilled.
Information density. Sorry, how much training is your AI going to have to do in order to be functional? Do you have a model that can bootstrap itself up from as much data as you can send in an unbroken transmission? Are you going to be able to access the hardware necessary to obtain more information? See above objections. There's terabytes of SETI recordings, but probably at most megabytes of meaningful data in there. 1% chance if undirected, 100% if directed, conditioning on all above conditions being fulfilled.
Inflexible policy in the case of observed risk. If the first three lines look like an exploit, I'm not posting it on the internet. Likewise, if an alien virus I accidentally posted somehow does manage to infect a whole bunch of people's computers, I'm shutting off the radio telescope before you can start beaming down an entire AI, etc, etc. (I don't think you'd manage to target all architectures with a single transmission without being detected; even if your entire program was encrypted to the point of indistinguishability from entropy, the escape code and decrypter are going to have to look like legible information to anyone doing any amount of analysis.) Good luck social engineering me out of pragmatism, even if I wasn't listening to x-risk concerns before now. 1% chance if undirected, 10% if directed, conditioning on all above conditions being fulfilled.
So if you were an extraterrestrial civilization trying this strategy, most of the time you'd just end up accomplishing nothing, and if you even got close to accomplishing something, you'd more often be alerting neighboring civilizations about your hostile intentions than succeeding. Maybe you'd have a couple lucky successes. I hope you are traveling at a reasonable fraction of C, because if not you've just given your targets a lot of advance warning about any planned invasion.
I just don't think this one is worth anyone's time, sorry. I'd expect any extraterrestrial communications we receive to be at least superficially friendly, and intended to be clearly understood rather than accidentally executed, and the first sign of hostility to be something like a lethal gamma-ray burst. In the case that I did observe an attempt to execute this strategy, I'd be highly inclined to believe that the aliens already had us completely owned and were trolling us for lolz.
*Why exactly did you click on a spammy-looking link in a comment on the topic of arbitrary code execution?