Having suggestions organized in contest form would only put pressure on them to impliment an idea regardless of if it is good or not. If they flat out said "We're not implimenting anything from this year's contest," there would be a lot of rage going around. You can make people sign agreements, but you have to realize that half the people wouldn't even read the damn thing. Even if they did they would still act however the hell they felt like if things didn't go their way.

On a side note, you can disagree with someone's ideas without acting immature about it. We do need people stepping in and saying "hey this idea is bad, and here's why," but when you resort to personal attacks/tag spams that have nothing to do with the topic; you're just going to end up getting yourself banned.