If you believe that there is something with arbitrarily high utility, then by definition, you will accept an indefinitely small probability of it.
Assume my life has a utility of 10 right now. My preferences are such that there is absolutely nothing I would take a 99% chance of dying for. Then, by definition, there's nothing with a utility of 1000 or more. The problem comes from assuming that there is such a thing when there isn't. I don't see how this is scope insensitivity; it's just how my preferences are.
Someone who really had an unbounded utility function would really take as many steps down the Lifespan Dilemma path as Omega allowed. That's really what they'd prefer. Most of us just don't have a utility function like that.
So you wouldn't die to save the world? Or do you mean hypothetically if you had those preferences?
I agree with the basic argument, it is the same thing I said. But Eliezer at least does not, since he has asserted a number of times that his utility function is unbounded, and that it allows for arbitrarily high utilities.
It has been claimed on this site that the fundamental question of rationality is "What do you believe, and why do you believe it?".
A good question it is, but I claim there is another of equal importance. I ask you, Less Wrong...
What are you doing?
And why are you doing it?