Facebook - Spammed Image tagging attacks

New image tag attacks may be surfacing as noted in this warning by PC Magazine:

New on Facebook: Image Tag Spam
http://blogs.pcmag.com/securitywatch/2010/12/new_on_facebook_image_tag_spam.php

QUOTE: There's always a new way to misuse complex software systems and Facebook is fertile ground for such things. The latest—at least I haven't seen it before—is image tag spam. This involves tagging a user on an image that contains spam content.  That user's friends will get a message that he was tagged, so you want to tag users with lots of friends. The image nearby is a test, but makes the basic point.

So how its it done? After all, you can generally only tag users who are your friends. In this case, the image belonged to a group which my friend didn't "Like" so it seemed out of the blue. We still haven't figured out exactly what happened; Facebook didn't respond to my inquiry on it and the image is still up in spite of my friend reporting it as abusive. But I think that either my one of friend's Facebook friends either did the tagging intentionally or one of them got his account hijacked.