In much the way scientists learned they could use minimal genotype data to identify "anonymized" individuals from pooled DNA samples, researchers have now determined that it is possible to ID anonymous users of social networking sites, according to this Technology Review article.
"The researchers wanted to see if they could extract sensitive information about individuals using just the connections between users, even if almost all of the names, addresses, and other forms of personally identifying information had been removed," the article says. "They found that they could, provided they could compare these patterns with those from another social-network graph where some user information was accessible."