I tripped across the daedalus project this morning while I was looking for player statistics for World of Warcraft. What a great site! The author, Nick Yee, has apparently been doing user surveys to MMOG players for years, and compiling various articles and statistics based upon them. The ones I've looked at so far are quite interesting!
Unfortunately it looks like I discovered his site a little late. There was a post on March 8th indicating he's not going to be updating it anymore.
Nevertheless, a treasure trove of data to comb through. Thank you Nick Yee, for putting this together and leaving it up!