Basic spam. Never ever reply, or click a link in one. There's a lot of that stuff out there, and there are lots of ways they can pick up your address. I delete about a dozen of them every day from my inbox, because my ISP's spam filter was filtering out some things that I wanted (even if the machine is 99% accurate, there's still that 1%, that is one e-mail out of a hundred that it throws out mistakenly). It was indeed removing a lot of spam, I found out when I asked the guys at the ISP to take me off the filter. But I'd rather toss out my own, and not miss something important. I suppose that they could be tempting to someone who was really interested in nude pictures of young girls, or getting a million dollars that isn't yours out of africa, but the first is easy to do without catching viruses and/or sending out spam from your own computer, not to mention a lot of other nasties, and the second ain't gonna happen: you just lose the contents of your own bank account.
If something seems too good to be true, it probably is.