Re:damn it (Score 0)

I think the solution should be based on time.

How often do you open an e-mail account; once maybe twice a year? Require the client to compute some sort of time intensive, single thread calculation. Keep in on the order of 10 to 20 minutes (maybe also give a simple flash game to play while they wait).

Legit users can wait the 10 min for their account but the spammers won't have the computational power to get enough accounts for spamming. Adjust the problem as processors speeds increase.