Well, I started now on every place where I have to give out an email address the following:
Let's assume for some reason you need to give your email address on
http://www.we-want-your-email-address.com/ .
Frist: I created a catch all account (should be a bit cryptic e.g.
w1s2j3b78@mydomain.com )
Second: Enter on that URL as email address:
we-want-your-email-address.com@mydomain.com
Third: Because you have a catch-all account everythin will be forwared to that one. Now when you receive spam you can easily identify where this email address has been gathered from and you can block that address!