Then I thought to turn off the account myself. And then I got this back from customer service.
"I appreciate the time you have taken to contact Match.com, and I'm sorry to hear that you're receiving unwanted messages from us.
I've issued a request to stop sending all Match.com emails to your [my email] address. Most messages should stop immediately. However, you may receive some promotional items for another 7 to 10 business days, and then those should stop as well.
I have also taken appropriate action regarding the Match.com account your email address was linked to. Although privacy policies do not allow me to reveal any details, I can tell you that these situations often occur when a member accidentally mistypes their email address when they register on our site.
Again, I apologize that this happened. If this issue persists or if I can do anything else for you, please reply to this email, and I'll be happy to help.
[First name, Last initial]
Match.com Customer Care"
So this is pretty interesting in several ways. When I turned off the account, I didn't change the password first. The original person who set it up, if they saved their username/password, can log in, reactivate the account and maybe connect it to their real email. If they don't, and keep using my email, I would presumably have received more email at that time. Possibly customer care has removed my email from this account -- I'm not necessarily interested in poking around the account in an effort to find out.
If Match.com were validating emails, there would be no "accidentally mistypes" happening -- you wouldn't be able to set up the account if you couldn't round trip it with the confirmation email, which is standard for online accounts in general (altho I'm encountering exceptions here, disqus, redbox, etc.). The idea that Match.com is preserving anyone's privacy in this interaction (given how I dealt with the problem) is exceptionally amusing. FWIW, there were no messages in the Match.com inbox (sent or received) or really anything at all. It was just a stub account and the only personalization was the Firstname fields filled in.