I received an email from Stack Exchange informing me of a recruiter's interest in my resume on Stack Overflow Careers. So far so good.
I responded at the Stack Overflow Careers site to the recruiter saying "Thanks, but no thanks".
The recruiter then follows up with a thanks to my response.
Stack Exchange sees that and sends me an email saying that the recruiter wants to contact me!
I realize that the bot is simply detecting a new message on the Careers site and notifying me. However using that heuristic alone is a tad simplistic. That can probably be applied only once per thread -- the first time.