Why do you ask for two email addresses?

The Email Address field is used for email notifications, Follow Lists and to email your password.
The Public Email Address field is what other users see when they view your profile. We realize that you
may not want everyone to know your real email address, but we need to know it in case you want to follow
certain content or if you want to have replies emailed to you. For this reason you can give us your real
email address in the Email Address field and only the Administrators of the forum will see it.

You can provide a different email address for the general public using the Public Email Address.
Some people like to put in something like example@no.spam.gmail.com. This way people can still
figure out what your real email address is, but spamming agents can't just parse through the page and
obtain your email address to spam you.