When I first read about Pascal's Mugging, it stuck in my brain. I knew that I had seen something like this occur in real life, though I couldn't quite place the specifics at the time. Then it hit me- chain letters are a classical example of this. They promise that if you copy the letter X times and distribute it, you will have good luck, your hair will grow back, etc., but if you don't distribute it, you will have bad luck, pianos will fall on you, etc.
I thought a little bit further about this, because I knew I hadn't originally gotten bothered about this sort of thing because of chain letters (no one sends actual mail anymore); chain letters are just the obvious example that will occur after five minutes of thought. The actual thing that had stuck in my brain was a phenomenon particular to the internet. On Youtube and 4chan, there are often messages posted at least superficially similar to the following:
In [year], [someone] was killed after [spectacularly gruesome details]. Post a copy of this message in the next 10 minutes, or the ghost of [someone] will find you tonight and [spectacularly gruesome details].
These threads have hundreds of replies almost every time that I see them on 4chan, and on Youtube they spread from one video to the next while actual comments become buried. This demonstrates that at least a significant fraction of the people that see these make the mental calculation that if they do not post it, they have a small chance of suffering incredible disutility, but if they do post it, they suffer only a few seconds of lost time. (They're also much more effective at spreading than chain letters because the transmission time and cost of spreading are much less than with chain letters).
This is one of the best examples of real-life Pascalian muggings that I've found and one of the arguments for the benefits of raising the sanity waterline- the lost man-hours to this sort of thing may be non-trivial. Also, this demonstrates one crude way of hacking the human brain in order to accomplish a task. Essentially, these postings and all of their variants are simple memetic mind viruses. In 4chan especially, they can be seen to outcompete actual posting when placed side by side. No one wants to be killed in spectacularly gruesome detail, and so they spread with ease and can dominate threads when the conditions are right.
Anyone else have examples of Pascal's Mugging or memetic viruses?