I've been looking at honeypots and I'm learning how to implement them on my app. Basically I'm building (well for the mean time until a better idea comes up.) is a "classified ad" site that doesn't suck and is a beauty to look at. And the problem I see with apps like these(or rather a subset of the main problem) is the amount of spam that gets fed into them everyday. Alot of interesting ideas flowing from this discussion.