We expect that post-singularity there will still be limited resources in the form of available computational resources until heat death.
Those resources do not necessarily need to be allocated fairly. In fact, I would guess that if they were allocated unfairly the most like beneficiaries would be those people that helped contribute to the creation of a friendly AI.
Now for some open questions:
What probability distribution of extra resources do you expect with respect to various possible contributions to the creation of friendly AI?
Would donating to the SIAI suffice for acquiring these extra resources?
Rewarding people for helping you isn't the same thing as extortion. Being generally pre-committed to never doing things to help another agent when you expect them to reward you for doing so seems like a bad plan.
You're right. I wasn't really commenting on that, I just figured punishment would be the next thing to come up after reward.