I guess perhaps I’m young and naïve, but why would you “cheat”? If your theme is horrible, you now have a top rated theme receiving more exposure showing how horrible of a themer you are…

What about a set panel of reviewers? Each theme could have a staff reviewer’s rating and a populous rating, then have the ability to sort a theme search by either of these ratings. That’d offset any artificial ratings boosting, you’d just have to trust your staff reviewers to know what they’re doing.

I like samer’s suggestion of splitting up the qualification, that’d be helpful.

If you can think of a truly cheat proof system, my hats off to you