That doesn't help if they sell your email though, because you don't know what company to match the spam with.

I use [email protected] for each service, and i catch every email regardless of mail address.

Sure they can manually fool me or use more sophisticated regex to find their service name (and i can obfuscate it), but in practically all cases i know which service has leaked my address if i get spam against a certain address that's not the service i signed up for.