Originally Posted by RazorSharpe

The idea is sound and I think with the right execution, almost all of the negatives mentioned by "that Spurs fan" can be negated.

Don't allow submissions to be made public - instead, have them emailed to you and YOU pick the interesting stuff and add your commentary and advice to it. This way, you stay motivated and your users don't have to wade through garbage.

Oli Gardener did something quite neat here:
35 Beautiful Landing Page Design Examples to Drool Over [With Critiques]

Perhaps you can do something similar with say:
- Choose home pages of a few sites and give your pros and cons on them
- Choose join pages of a few sites and give your pros and cons on them

This will obviously be very generic to the point where anyone with a site can apply your best practices feedback and come away with something worthwhile.

For those saying the don't or won't give their ideas away; fair enough. I think the point here should be getting already realized ideas critiqued so that you can squeeze more out of it. Or taking existing concepts and re-conceptualizing them so they become fresh and current.