Why would anyone want to work with/fund EY if it was his own volition that was being implemented?
If 10 people work together with EY or fund him, they can agree on a combination of their utility functions, and each will get 1/11th of the universe to rule over. That's a far cry from implementing the CEV of all humans who have ever lived.
It's much easier to get donations and avoid potential political problems (like the US government intervening) if EY is implementing the CEV of all humans rather than the CEV of everyone who donates. If EY seems like a mad scientist hellbent on taking over the world for himself and a small group of people, many people will treat him appropriately. Just think about your gut-level reaction to hearing "EY wants to implement CEV for only SIAI volunteers and donors" and to "EY wants to implement CEV for all of humanity."
Note: not that there won't be any political problems with CEV for all humans. Rather that pushing for CEV for a small group of people will cause more problems in this arena.
Taken from some old comments of mine that never did get a satisfactory answer.
1) One of the justifications for CEV was that extrapolating from an American in the 21st century and from Archimedes of Syracuse should give similar results. This seems to assume that change in human values over time is mostly "progress" rather than drift. Do we have any evidence for that, except saying that our modern values are "good" according to themselves, so whatever historical process led to them must have been "progress"?
2) How can anyone sincerely want to build an AI that fulfills anything except their own current, personal volition? If Eliezer wants the the AI to look at humanity and infer its best wishes for the future, why can't he task it with looking at himself and inferring his best idea to fulfill humanity's wishes? Why must this particular thing be spelled out in a document like CEV and not left to the mysterious magic of "intelligence", and what other such things are there?