Without a reason to attract (relative) experts beyond philanthropy I think there's a risk that a ballooning amateur/expert ratio could soon cripple this, as happened to the way Matasano Crypto Challenges used to be run.

I hate to be critical as I like the idea, and obviously there's some utility in it for experts as it is but it's much, much less so than for amateurs, and there's no reason to think that this imbalance won't manifest itself sooner or later. I feel this stands a much better chance of solving (or contributing to solving) the education problem and getting good traction if it was positioned to solve a much more general problem - like snippet management - in a really, really good way, and tacked these features on the side.