Rick,

you are aware the the registration process and spamming is fully automatic? There are no person sitting there going trough registration manually, just a computer buzzing away with some pretty nifty spam-software.
The only way to stop spamming is having an input field and some graphical element showing something only a human can recognize. The input field must be filled with the correct information before the new user is accepted. This only works until the spammers software get advanced enough to decipher the information in the graphical element.. Then it's back to square one (until legislation and law-enforcement kicks in, which is the real solution to this).