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?
That is more-or-less my own analysis. Notoriously:
CEV may get some the votes from the poor - but offers precious little to the rich. Since those are the folk who are running the whole show, it is hard to see how they will approve it. They won't approve it - there isn't anything in it for them. So, I figure, the plan is probably pretty screwed - the hopeful plan of a bunch of criminal (their machine has no respect for the law!) and terrorist (if they can make it stick!) outlaws - who dream of overthrowing their own government.