Read the article. It was a hoax/prank. The point was on FB you can now be added to a group without your knowledge or consent.
From the article,
“Blogger Michael Arrington seems to have already performed a helpful proof-of-concept by adding Mark Zuckerberg to a group supposedly representing NAMBLA, the North American Man-Boy Love Association. Zuckerberg’s addition to the group is broadcast to all of his friends, as shown in the image above.”
“Though some have questioned Calacanis’s story, Facebook’s own FAQ confirms that anyone can be added to a group without his or her consent: “Can I prevent people from adding me to a new group?” is answered by “’The functionality of approving a group membership is not available.’”
Sophos’ Wisniewski argues that the prank could have serious consequences. “’Imagine you are traveling to the United States from overseas and your friends find it amusing to add you to a group that looks terrorist related,’” he writes. “’You might find a welcoming committee from the border patrol that you weren’t expecting.’”
That's one of the reasons why I left FB after having been on it three weeks, back in 2013.