You should first ask yourself if you really need an email address. And see if you can get away with not having one.
Requiring that the user have an email on file is not as necessary a requirement as a lot of people seem to think. It seems like half the time or more, they just want to spam it anyway.
As someone else mentioned in the thread, make the email address optional, with the understanding that without it they can't recover lost passwords.
This is probably an unacceptable solution for some sites, but I can definitely think of cases where the only reason you need email is for password recovery, and account loss isn't the end of the world.
Requiring that the user have an email on file is not as necessary a requirement as a lot of people seem to think. It seems like half the time or more, they just want to spam it anyway.