Looks like there's a Great Hatsby variant scraping the feed of recent LJ posts and looking for people with visible AIM screen names, then randomly initiating a connexion between two users (though, unlike Great Hatsby, it doesn't appear that the two users are sent the same initial message).

If you receive an IM from the user devourablesalmon, there is another human being on the other end who is probably rather confused. You may wish to point him/her at this post by ericjay to explain what's going on.