I can tell you that there are a lot of sites I use that ask for my email address and I'd rather not give it to them, and I can tell you that I give them crap.

I can tell you that there are a lot of sites I use that ask for my email address and I'd rather not give it to them, and I can tell you that I give them crap. I.e. I give them an address I've set up specifically for the purpose of giving it to sites that require one. There's an awesome, self-explanatory site called 10minutemail.com that I love using; sites can ban their domain (I think some do) (but it's a new one every month), but there's no way a site can tell the difference between my real Gmail account and my crap other Gmail account. And I think a lot of people use similar tactics. In other words, requiring an email address doesn't mean users will give you their email address. I only give my actual address when I want to. Meanwhile, it's a pain when a site requires one, and sends me an email with a confirmation link. I feel alternately clever (ha, I outsmart them) and sleazy (this probably isn't what they intended), and always annoyed, when I do this. I recommend making emails optional (but if it has a definite use, like for resetting a password, then explain this to the users). I was happy, kind of exhilarated actually, when I signed up on Hacker News and all it asked for was a username and password; the email address is a text field that one can fill out when desired. I think I remember it explaining that this address wouldn't be visible in your profile; it would just be used for notifications about your account, or something. Take note.