They're all in the form of bounces, and sometimes the emails even apologize that your (alleged) emails are bouncing because they (the spammers) are getting so much spam themselves (which is kind of clever).
They're all to (pretend my domain is domain.com) email@example.com, or something similar, which makes me think that my address didn't get out, but that it's a fishing expedition using whois.
Maybe my ISP is slipping, or those feckholes have figured out some evil trick.
Update: Crap. I realized what's going on. They're not fake bounces -- Those dirtholes are slapping random user names on my domain and using the addresses for the reply-to/from headers of the messages.
\t : iPhone->you