I like this "hackers in need idea". Though there needs to be a way to keep out the leechers/time wasters. A turing test of sorts or captcha for programmers?? Dunno...
You can require anyone trying to sign up to complete a reasonably difficult programming problem. It could either be sandboxed on the server, like Facebook's engineering puzzles, or require a short output like Project Euler. This would drive away people who can't do FizzBuzz and nontechnical people who want to hire someone to make Facebook for dogs or whatever.
