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At MIT, an experiment identifies which students are gay, raising new questions about online privacy

By Carolyn Y. Johnson, Boston Globe, September 20, 2009

It started as a simple term project for an MIT class on ethics and law on the electronic frontier.

Two students partnered up to take on the latest Internet fad: the online social networks that were exploding into the mainstream. With people signing up in droves to reconnect with classmates and old crushes from high school, and even becoming online "friends" with their family members, the two wondered what the online masses were unknowingly telling the world about themselves. The pair weren�t interested in the embarrassing photos or overripe profiles that attract so much consternation from parents and potential employers. Instead, they wondered whether the basic currency of interactions on a social network - the simple act of "friending" someone online - might reveal something a person might rather keep hidden.

Using data from the social network Facebook, they made a striking discovery: just by looking at a person�s online friends, they could predict whether the person was gay. They did this with a software program that looked at the gender and sexuality of a person�s friends and, using statistical analysis, made a prediction. The two students had no way of checking all of their predictions, but based on their own knowledge outside the Facebook world, their computer program appeared quite accurate for men, they said. People may be effectively "outing" themselves just by the virtual company they keep.

"When they first did it, it was absolutely striking - we said, Oh my God - you can actually put some computation behind that," said Hal Abelson, a computer science professor at MIT who co-taught the course. "That pulls the rug out from a whole policy and technology perspective that the point is to give you control over your information - because you don�t have control over your information."

The work has not been published in a scientific journal, but it provides a provocative warning note about privacy. Discussions of privacy often focus on how to best keep things secret, whether it is making sure online financial transactions are secure from intruders, or telling people to think twice before opening their lives too widely on blogs or online profiles. But this work shows that people may reveal information about themselves in another way, and without knowing they are making it public. Who we are can be revealed by, and even defined by, who our friends are: if all your friends are over 45, you�re probably not a teenager; if they all belong to a particular religion, it�s a decent bet that you do, too. The ability to connect with other people who have something in common is part of the power of social networks, but also a possible pitfall. If our friends reveal who we are, that challenges a conception of privacy built on the notion that there are things we tell, and things we don�t.

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See also Facebook Data Mining: Truth in Association?