If you don’t use SpamGourmet or a similar service I highly recommend them. They allow you to create unlimited e-mail forwarding addresses that can be created on-the-fly — allowing you to easily detect which websites are giving out your information. Definitely get an account if you don’t have such a tactic already!
Fiddler, a great Windows (web) proxy gave out e-mail address. I’m sure it was in their terms of service that I didn’t bother reading. Still disappointing.