What do you mean by that? An email address does not uniquely identify one person.
it can be useful for communications.
Indeed, especially for spam marketers.
If you make me provide an email upfront I'm probably going to ignore your site or at best give you a temporary address. The only services that have my real address are ones that have proven their value to me. If you can't do that then chances are all the data I provide your service will eventually end up in the wrong hands anyways.
Comments
it's unique
What do you mean by that? An email address does not uniquely identify one person.
it can be useful for communications.
Indeed, especially for spam marketers.
If you make me provide an email upfront I'm probably going to ignore your site or at best give you a temporary address. The only services that have my real address are ones that have proven their value to me. If you can't do that then chances are all the data I provide your service will eventually end up in the wrong hands anyways.