Looks like there are some large scale joe-job attacks going around. I get so many spam emails from addresses that are so obviously faked. It's inconcievable to think that owners of some of these adresses would resort to spamming.
In the strictest sense a joe job is to 'forge' an email so that all the headers look like it came from an innocent party. What most spammers do is that they fake the From and Reply-To fields in the spam message. That way they don't get their own addresses (which are 'disposable' anyway) into any blacklist. Yet thousands of perfectly innocent people who wouldn't dream of sending spam to their worst enemies get placed in these black lists simply because of the faked headers.
However since people have all kinds of anti spam measure - many of them half baked running on servers and desktops a simple fake headers is almost as effective as a proper joe job in getting an innocent into loads of black lists.