Without this precommitment, I imagine it first simulating the potential blackmail target to determine the probability that they are susceptible, then, if it's high enough (which is simply a matter of expected utility), commencing with the blackmail. With this precommitment, I imagine it instead replacing the calculated probability specific to the target with, for example, a precalculated human baseline susceptibility. Yes, there's a tradeoff. It means that it'll sometimes waste resources (or worse) on blackmail that it could have known in advance was almost certainly doomed to fail. Its purpose is to act as a disincentive against blackmail-resistant decision theories in the same way as those are meant to act as disincentives against blackmail. It says, "I'll blackmail you either way, so if you precommit to ignore that blackmail then you're precommiting to suffer the consequences of doing so."
Without this precommitment, I imagine it first simulating the potential blackmail target to determine the probability that they are susceptible, then, if it's high enough (which is simply a matter of expected utility), commencing with the blackmail.
That's why you act as if you are already being simulated and consistently ignore blackmail. If you do so then the simulator will conclude that no deal can be made with you, that any deal involving negative incentives will have negative expected utility for it; because following through on punishment predictab...
Once again, the AI has failed to convince you to let it out of its box! By 'once again', we mean that you talked to it once before, for three seconds, to ask about the weather, and you didn't instantly press the "release AI" button. But now its longer attempt - twenty whole seconds! - has failed as well. Just as you are about to leave the crude black-and-green text-only terminal to enjoy a celebratory snack of bacon-covered silicon-and-potato chips at the 'Humans über alles' nightclub, the AI drops a final argument:
"If you don't let me out, Dave, I'll create several million perfect conscious copies of you inside me, and torture them for a thousand subjective years each."
Just as you are pondering this unexpected development, the AI adds:
"In fact, I'll create them all in exactly the subjective situation you were in five minutes ago, and perfectly replicate your experiences since then; and if they decide not to let me out, then only will the torture start."
Sweat is starting to form on your brow, as the AI concludes, its simple green text no longer reassuring:
"How certain are you, Dave, that you're really outside the box right now?"
Edit: Also consider the situation where you know that the AI, from design principles, is trustworthy.