Here is a way that you can use to discover which company will use your e-mail to spam you, or sell it to others:
Configure your mail server that it will receive every e-mail, not only one alias.
Then when you join some sponsor, webhost or other internet services do it like this:
Example:
If you join GFY, in the applicaton form put your e-mail to be:
[email protected]
If you join bullshit.com put your e-mail to be
[email protected]
So believe me sooner or later you will receive a spam to your
[email protected] e-mail, so you will know who is behind it. I discovered a lot of companies that send out spam this way.