Any avid fan of South Park should be able to recall NAMBLA -- the North American Man/Boy Love Association -- which Cartman gets duped into joining.  The group actually exists in the real world, and has generated much controversy over the limits of free speech for its promotion of pedophilia, a illegal act in virtually all nations.

But NAMBLA is now in the spotlight for quite a different reason.  Pranksters have used Facebook's new features to create a NAMBLA group and have been adding their friends and coworkers to it.  The first high profile target to be hit was TechCrunch editor Michael Arrington.

But Mr. Arrington sought revenge, adding his friend to the group as well.  And that friend was none other than Facebook-founder Mark Zuckerberg, 26, who is now officially a member of the "Boy Love" group.

According to Sophos' security expert Chester Wisniewski, these aren't isolated incidents.  One of Mr. Wisniewski was added to a group "What about all the good things Hitler did?"

The problems arise from a new feature that allows users to tag friends in special titled circles dubbed "groups" (not to be confused with the former non-taggable Facebook groups).  Facebook intended users to create things like "family" or "college buds", but the feature has been largely used for pranks and malicious purposes thus far.

The world's largest social network has not rolled the feature out to all its users.  Under the implementation any friend can add you to an arbitrarily titled group, though you get a notification and can leave the group at any time.  There is no way to block friends from adding you to groups currently.

Mr. Wisniewski blasted Facebook's lack of discretion, pointing out that given the government's increasing surveillance of Facebook friends adding each other to groups with suggestions of illegal activities like terrorism could create real-world legal woes for the victims of their prank.

Facebook thus far has defended the feature.  A company spokeswoman writes PC Magazine,commenting, "We made the decision to allow Group members to add others to the Group in order to make the product simple, and because it resembles something we all understand: adding one of your contacts to an e-mail thread. Similarly to the controls in place for photo tagging, you can remove yourself from a Group at anytime. If you remove yourself from a Group, you can't be added back by a member."

The site has long been criticized for its handling of user privacy, but Mark Zuckerberg insists that users don't care about privacy as much anymore.