Not right now. Maybe in the future we'll let you join using e-mail, but for now it makes it a lot easier to prevent people from faking their own profiles and it also speeds up the process of adding friends.
"CupidWithFriends would like to access your public profile, friend list, email address, custom friends lists, birthday, current city and your friends' relationships, birthdays, current cities and photos." -> Cancel
(In general, I don't feel like Facebook should let me give my friends' photos [not just mine, but theirs] away to a 3rd party without their explicit consent first).
Relatedly, the 'Why Facebook' hover text says:
"We use Facebook to make it easy to see which friends use the service, add existing friends, and prevent certain friends from seeing your profile. We do not post to your wall or spam your friends."
So my friends who I don't want to have see my profile will know I'm hiding it from them? Because they'll know I'm using the service, but they can't see my profile?
