The simplest known complete representation of my utility function is my brain, combined with some supporting infrastructure and a question-asking procedure. Any utility function that is substantially simpler than my brain has almost certainly left something out.
The first step in extracting a human's volition is to develop a complete understanding of the brain, including the ability to simulate it. We are currently stuck there. We have some high-level approximations that work around needing this understanding, but their accuracy is questionable.
Assume you have a working simulation. What next?
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?