I tend to go either way when building a site, depending on the market and how people are going to interact with the site and with others. On sites with kids, using real names is a BIG turn off and if it isn't clear how the name will be used, people will pass.

It's anecdotal, but I use my real name in many places (not ycombinator, ironically), but my wife never will. If she can't choose some sort of display name, she will pass or use fake info.

Also, you might want to check out Smashing Magazine's recent survey of signup web forms. They touch on this a little bit. They don't give much other than statistics, but it might lead to some good discussion. http://www.smashingmagazine.com/2008/07/04/web-form-design-p...