So when amazon first started they asked your email address as your account name. Then they got bigger, started to have concepts of profiles and wishlists and like and they allowed for you to click a button that would keep you email address hidden in your profile. however your "nickname" or username is always public, so if your username is your email address, even if you've clicked keep my email address hidden, people can still see it. It's fairly easy to go change your "nickname" but I'm not sure how long this was true before someone emailed me about one of my reviews.
I mostly don't care, but I know there are some of you out there that are a bit more protective about your email address, so I thought I would let people know.