Problem is, I end up getting subscribed to mailing lists all the time because a lot of people with the same last name and a similar first name don't pay the fuck attention to what address they're typing in.
THIS! I have a rather regional last name... it's not common. But every moron out there seems to think it's theirs. I've done a lot of the same things that others have done... responded, canceled, ignored, etc. I've even tried to get the sources of these to require a confirmation link be sent to the subscribing email... no luck there either.
Also, GMail is very good at catching SPAM, in my experience. Every once in a while, I'll get a few that I report and from then on, I don't see them anymore.