My identity has been stolen (a little)

Well, it appears i am now officially a victim of identity theft. Yesterday i got one of those "returned mail" messages in my inbox, but i didn't recognize the address that the message had been sent to - and when i saw the subject line i knew i hadn't sent it. I e-mailed Yahoo about it (which by the way i've loved using yahoo mail for around 7 years now), and they said it looks like someone's managed to falsify the "from" or "reply-to" section of a spam e-mail that they sent. So now it looks like i sent the message. Worse, it appears that there's nothing Yahoo can do to find out who's doing this or to stop them. So all i can do is delete all the returned messages that come to me and pray that my legitimate messages don't start getting filtered out by spam blockers.

I guess it doesn't do you much good to know this, since i don't think there's a way to prevent it, but I just wanted everyone to know that the return address on the spam you get could be that of another innocent bystander.