I Love the idea (it does sound familiar..), just a couple nitpicks:

1. Please don't make me sign in with Twitter. Not everyone has a twitter account and not everyone wants to give you access to theirs.

2. I'd like to be able to rate ideas right from the leaderboard. If i'm just browsing and i see an idea i think is excellent i'd want to be able to tell them that.

3. The design struck me as a generic blog design. I'm not sure exactly what it was, but it looked like a generic wordpress blog at first glance.

Other than that, i like it. Good luck!