We (the mods) have actually talked about this before.  We decided that ultimately that was too messed up a thing to do.  I know that can seem arbitrary (But you do employer reviews!!) but in our experience, the number of freelancers ripping off employers is dwarfed by the number of employers looking for slave wage artists.  The best thing you can do as a potential employer is to do a little research.  Speaking from the perspective of someone who actually does hire people fairly regularly, you should really be trying to hire the people with the best attitude and best reputation, not necessarily the best portfolio.  That is a lot harder to ascertain, but artists who regularly scam their clients tend to have a hard time staying all the way under the radar.  Use google and your own professional networks to minimize your risk, because a yes/no curated list of artists is really not something we can ethically provide.

Should start "marketing" or "buzz" or whatever for it in a few weeks I hope.  It's going into beta this weekend finally, been on it for a long time...but it's starting to look like a real game!

ok, rewrite complete, thanks for the feedback guys, I really appreciate it!  http://www.gamasutra.com/blogs/AdamSaltsman/20090724/2571/Pixel_Art_Freelance_Best_Practices__Guidelines.php

noted!  I'm gonna keep collecting feedback all the way through the weekend, so keep it comin!

wouldn't it be cool if I made this a contest rather than just hiring someone

NO.