While you may consider user e-mail addresses to be public, some people take umbrage when their e-mail addresses are disclosed.
Personally I use a different e-mail address for almost every site, so searching by e-mail address wouldn't find my account, but I know many people use the same e-mail address for several things.
Personally I use a different e-mail address for almost every site, so searching by e-mail address wouldn't find my account, but I know many people use the same e-mail address for several things.