For those just starting to sign up for tournaments, camps, or anything baseball related, use tags in your email.
For example if I were baseballdad@gmail.com and I created a PG account, I would use the email address baseballdad+pg@gmail.com. Using + and a tag after is allowed with email.
You can then keep track of who is selling your info. If you get a camp invite addressed to baseballdad+pg@gmail.com, you know what happened. A much easier way to do this is if you own your own domain name (this is what I do).
Then depending how much of a pest you want to be you can setup auto forwarding rules....;-)