Okay, leeneia, I'll tell you a likely source for spammers and virus-sending pricks to acquire your e-mail address and use it to masquerade their crap and pretend it's coming from you.
We all have e-mail friends and acquaintances that forward jokes, glurge, cutesy angel graphics and e-snowball fights, "inspirational stories", urban legends, virus warning hoaxes ("just in case it's true") and chain letters (Damn them! Delete them all unread and end the stupidity!), etc. ad nauseum. Without fail, they hit that damn "FORWARD button in the e-mailer that I wish would disappear from all e-mail software. Then they put a whole whack of e-mail addresses in the TO: box and send it out to everybody, many of which will repeat the same process.
After several generations, you get a basically unreadable collection of text broken up by >>>s, along with a whole pile of headers containing and broadcasting every e-mail address the thing has been sent to in the last month and a half. Who knows where these e-mails end up?... with your (and several other, including the senders) e-mail address on it for the harvesting by someone who collectes, uses and sells e-mail address, almost never for honourable purposes.
If people want to send stuff out to many recipients and it is a message that is likely to be passed on to others, they should enter those addresses in the BCC: box. That is, the BLIND CARBON COPY field, where you can't see where the emails are bound. And above all, DON"T use that c___s___ing FORWARD button. Cut and paste the message to a new e-mail and clean it up, for chrissake! If you're going to send it out, have some courtesy to make it readable.
One more tip... You know those webpages that have a link that says "CLICK HERE TO SEND THIS PAGE TO A FRIEND"? Well, don't! If you want to alert someone to a webpage, cut and paste the URL to the message body of a regular e-mail. Don't give a friend's e-mail address to god-knows-who so they can sell it to spammers.
Imagine the uses your e-mail address could be put to, besides just to fill your inbox with spam... Maybe for jollies some scum posts some kiddie porn on a newsgroup with your e-address in the REPLY TO: field. Suddenly you're inundated with hate e-mail. Probably the authorities would ignore it and spot in the header that it didn't come from you, but maybe they deceide to check you out just in case you might have some tenuous link to this kind of crap. Maybe they show up and check out your hard drive. Is everything completely above board there, or do you have a pirated game there or maybe a demo of some software you didn't pay for and should have deleted months ago or maybe some MP3s you don't have the original CDs for, etc...
All because Aunt Martha can't stop forwarding little angel graphics and chain emails around to the Quilting Guild and you too.
Okay, maybe I'm getting paranoid, but it's not completely outside the realms of possiblity.