A common rebuttal to proponents of online privacy is to just not share personal information with services like Facebook, Twitter and the like. It's a solid argument, but one that's not practiced, even by those with privacy concerns.
The researchers point out that Facebook's relatively new sharing system that allows "friends of friends" to see posts may be leading to this increase in sharing. Some users obviously don't like that, but it seems that most don't even notice. Most of us would like to think "friends of friends" would overlap with our own personal friend list. That's usually the case, but it can sometimes lead to awkward situations where people you don't like suddenly being able to comment on statuses that have a mutual friend tagged in it.
It's these situations where Facebook's privacy controls could be more refined to prevent accidental shares with unwanted parties. That being said, the social network's privacy controls are apparently sufficient enough for the average user. Why would they share so much of their lives if it wasn't?[h/t: Huffington Post]