I don't know if this issue has been raised before, but Facebook just released improvements to make it easier to use Facebook connect, and I think PGV would be a great addition. Myself and several of my users would use this feature. You can read their blog post here: http://developers.facebook.com/news.php?blog=1&story=310
The way I envision it: instead of a new account request, they could login with a "Facebook" button, which would authenticate through FB with their own credentials. If the user doesn't exist in PGV, possibly some generic name would be created in the database so that Admins could still confirm the user and grant access. In addition, their Facebook profile picture (or another Facebook picture of their choosing) could be automatically substituted into their individual page and on charts, along with a link to their FB profile.