In a stark reversal from how people used to use the social network, more than half of users in a recent study had hidden their friends lists from public view.

Facebook users have dramatically altered their behavior in recent years to make their profiles less public, according to a study presented last week at the 4th IEEE International Workshop on Security and Social Networking.

In March 2010, only 17.2 percent of users hid their friends list. By June 2011, more than half (52.6 percent) did so. Researchers at the Polytechnic Institute of New York University got their data by crawling 1.4 million Facebook profiles from New York City two times, 15 months apart. Then they checked to see how people's behavior on the site had changed during that interval.

The move to privacy was not quite evenly distributed across the populations. "We have found that women tend to be more private than men, and that young and middle aged people tend to be more private than older users," the researchers explain. "We have found that people living in the wealthier boroughs and in boroughs with more US-born users tend to be more privacy conscious."

One small point to highlight regarding our continuing series, Kids Are Not As Dumb About the Online World As You Assume: younger people employ Facebook's privacy controls to a greater degree.