I just want to throw in the concept of "voter apathy". In my opinion it's why all voting systems, liquid or not, are doomed to fail (or at least be very inefficient). Even delegating one's vote to a relevant expert would require some research, for which there is no good reason in such a system. (there might be social pressure to delegate one's vote the "right" expert though, somebody who appears competent on a superficial level (i.e. talking a lot), but who's voting history might not reflect that competence)
I think, delegating one's vote to a known expert would actually be a problem, not a solution. Just delegate it to a friend you trust, that knows more about some stuff than you do. He then may use your vote directly or delegate it further to someone he trusts.
What I fear in liquid democracy system is PR efforts that will be done to market "experts".
