I don't wanna be an #@!%!#% here, but ehh... I think the "5 BTC for FREE!" thing, is kinda... flawed...
"flawed" ??I've been telling people it is a half-baked, I've-lost-my-friggin-mind idea!
So far, I count it as a big success-- I've learned a lot that will help me with my next Bitcoin-related project, I've made a bunch of people a teeny-tiny bit happier, and I've personally invested just under $1.00 worth of bitcoins over the last two weeks.
I did throw in the towel today and turned on reCAPTCHA for everybody getting bitcoins (it looks like somebody DID bother to write a robot to harvest coins through proxies). It was fun trying to come up with new, creative ways of detecting cheating, but I have more important things to work on.