Personally I think what is needed here is a two tier system.  The first tier is for folks who want to upload models, textures, etc and just have people who download them.  They can upload as much as they want when they want but they wouldn't be eligible for revenue sharing.  The signup process would be just as the site does now, with little verification or requests for personal information, and you could always leave them the "donate via paypal" button in case someone wanted to donate to them for their work.

The second tier would be a little harder to qualify for, and this would be those folks who want to take part in revenue sharing.   The amount of information required would go beyond just a simple email address and paypal account. Your IP would be logged (not foolproof, granted, but it cuts way down on multiple account abuses) to start with and you could not start a duplicate account from the same ip address.

When you sign up to be considered for revenue sharing, your submission would be reviewed for quality.  At first this could be done by the admins, and later on once you have a few people who qualify as revenue sharing "vendors" for lack of a better term, you could allow them to volunteer to help in this vetting process.