Every once in a while I need to register my email address on a website in order to be able to access their material. They will require either a username or First and Last name.
What I do is put their site name in those fields rather than my name. For example, to access free crochet patterns I may have to register on "Zippy Crochet" dot com (fake name by the way). I will enter Zippy as my first name and Crochet as my last name and then provide my email address.
If I start getting marketing emails from different companies with a "Dear Zippy" header I'll know Zippy Crochet sold my address out.
You probably already know this tip but I hope someone finds this tip useful!