as to why they could be passing captcha's, there is a site that has been helpful to blind and partially sighted users who can't solve captchas due to not being able to see them, that the spammers could be using. Its a firefox plugin.
the technology is supposed to be for blind users, not spammers, and it uses humans to help solve captchas, but just an idea, spammers could be using that.
Even so, they wouldn't be able to get past the email verification step.
Edited by White and Nerdy on 04-16-12 12:35 PM. Reason for edit: No reason given.