There is a great deal of research being done by a Toshio Yamagishi
at Hokkaido University. His web page is here
http://lynx.let.hokudai.ac.jp/members/yamagishi/english.htm

His most recent paper, which is relevant to your discussion is not
yet on his site, but I can get it for anyone who is interested. He
is a social psychologist and does a study of reputation systems. He
uses an online open market where people create sell and buy things.
They can lie about the quality of what they sell or can tell the
truth. He test four reputation models. Completely identified where
you can't change your nym. Completely anonymous. Positive reputation
tracking only where you can change your nym and negative reputation
tracking with changing nyms.

He finds that complete identity is the highest quality of exchange,
but this is obviously only possible in a closed community and not
something I believe is feasible or desireable on the Net. Completely
anonymous is obviously bad. The two interesting results were that
negative tracking started out with better quality and quickly
degenerated while tracking positive reputation started out rather
low, but grew until it was almost a high as a closed system with
full identity.

Quality here is defined as the likelyhood of buying something of
lower quality and marked, or of someone lying. What he shows is that
onces people develop positive reputations, they continue to try to
keep them while negative reputation tracking encourages reseting
your nym. Negative reputation SOUNDS good so people try not to get
it at the beginning, but what really affects our behavior long term
is positive feedback.

His research is very thorough using a variety of time-lines and
techniques in a laboratory with real people an a mocked up B2B
exchange.