by Larry Magid

This article first appeared on CNET News.com

Last week, Facebook announced its new Groups feature, which is designed to limit some of your communications to a subset of your Facebook friends. But there is the danger that you could actually be talking to lots of people who aren’t on your Friends list at all.

In an interview, Facebook CEO Mark Zuckerberg said, “There are a lot of things you want to share with all your friends at once, but there are also things that you only want to share with your family or some co-workers. If you don’t have a way to do that, you just won’t share them at all.” He said that he expects “that a lot of people will use Facebook as their tool to communicate and stay in touch with these groups of people that are really important to them.”

But when it comes to privacy, Groups is a double-edge sword. If you’re not careful, you could easily wind up sharing information with complete strangers.

In theory, Groups provides users additional privacy, because anything you post in a group is seen only by members of that group, which can be a much smaller group than your entire list of Facebook friends. It could be your running group, the people at work, or perhaps your immediate family.

But in practice, groups can quickly get out of hand because any member of a group can add members from his or her own friends list, even if they’re not friends with anyone else in the group, including the group’s administrator. So, if you create a group, let’s say your baseball team, there is nothing to stop the left fielder from adding his cousin who isn’t actually on the team. And once his cousin is in, he can add friends of his own so that a 9-person baseball team’s group could grow big enough to fill a ballpark.

I know about this firsthand because the day after Groups was launched, I was invited into what started out as a small group, but soon people in the group started adding their friends and within hours it grew to several hundred members, including a lot of people I don’t know.

Managing Groups
There are ways to manage Groups. Members of the group can always see who else is in the group and remove themselves if they don’t want to be there. Also, the administrator (by default, the person who created the group) can remove people from the group, but only after the fact. The administrator does not get to approve or reject new members.

Also, people who are added to groups by others don’t get a chance to either accept or reject the invitation. They’re added immediately and their name shows up on the roster unless and until they remove themselves. Zuckerberg was  reportedly added to (and later quit) a group pretending to represent NAMBLA–the North American Man/Boy Love Association.

Another issue with groups is that, by default, the membership list is public information, though there is a way to create a secret group.

There are three types of groups: Public, Open, and Secret.

• Public: groups where both the membership list and the contents of the group is accessible to anyone.
• Closed: groups–the default setting–where the contents are private but the membership list is public so it’s possible to search for Closed groups and know who is in them. And when you are added to a closed group, that information may appear on your News Feed.
• Secret: groups where the member list, the contents, and the existence of the group are secrets to anyone other than the people in the group.

Another annoyance with groups is that, by default, all messages posted to the group are sent to the e-mail address associated with each member’s Facebook account. That can be a good feature if the traffic level is moderate, but it can get overwhelming. Fortunately, that can be turned off by clicking “Edit Settings” when you’re on the Group’s page.

Know the Groups you’re in

When someone adds you to a group, you will get an e-mail that includes a link to the group’s Facebook page. Click on that link to make sure it’s a group you want to be in. If not, click “Leave Group” in the upper right corner. You can also see what groups you’re in from the left-most column on your home page.

You should periodically click on the “See All” link near the top left of any Group you’re in.  If you don’t want to be sharing information with people on that list or if you’re not comfortable being associated with that group, you should consider leaving the group.