I have heard mixed opinions on this in the past. Do you think when a domain name is transferred especially to a new registrar with new contact info if it can effect your SERPS listings and if backlinks especially in Google may be discounted? Also can the site lose it's PR? I have had very limited experience with this so it is rather hard for me to tell but maybe those who have been buying/selling for a while can clear this up, thanks!
Nobody has really shown this to be anything that you should really have to worry about. It's probably just another one of the many rumours.
From what I've seen, Yahoo and MSN don't care about transfers; Google does (although, it appears to affect lower PR sites more so than the sites with high PR). PR decreases (or goes to zero). However, because the links stay in place, your non-search traffic does not change. As long as the new owner maintains the site quality, PR will come back.