Doesn't iteration cause this strategy to be balanced out? After it becomes clear that two players have an unbreakable alliance, it's in the best interest of the rest of the players to destroy those two first in all future games.
This passage from the TV Tropes page on the Scrub is relevant:
The mistake the Scrub often makes is making up rules too soon. The Metagame can often turn an apparent imbalance on its head. A lower tier character can become a higher tier one, or vice versa. Or something that seemed initially very unbalanced can be countered with time and effort at learning the tactic. The Scrub circumvents this by simply banning the practice without making a good faith effort in actually getting around it with the in-game rules.
I'm surprised that you didn't bring up what I find to be a fairly obvious problem with Cryonics: what if nobody feels like unthawing you? Of course, not having followed this dialogue I'm probably missing some equally obvious counter to this argument.
"But isn't Eliezer suggesting, in this very post, that we should use uncommon justified beliefs as an indicator that people are actually thinking for themselves as opposed to copying the beliefs of the community? I would assume that the standards we use to judge others should also apply when judging ourselves.
On the other hand, what you're saying sounds reasonable too. After all, crackpots also disagree with the consensus of a respected community."
Eliezer didn't say that we should use "disagreeing with the consensus of a respected community" as an indicator of rationality. He said that we should use disagreeing with the consensus of one's own community as an indicator of rationality.
It's really only applicable to forms of cheating which can be countered by non-cheaters ganging up on the cheaters. If the cheat causes an automatic win in every game, the scrub argument against its banning doesn't apply.
But I agree, I was assuming iteration. Obviously, the scrubbiness of the rule against unbreakable alliances (and thus the cheatiness of the tactic), would depend on metagame circumstances.