For all you PGP fanatics, consider (from http://33bits.org/2011/03/09/link-prediction-by-de-anonymiza..., a blog which I highly recommend) the sentence "During (...) 2007-2009, Shmatikov and I (...) showed how to take two graphs representing social networks and map the nodes to each other based on the graph structure alone—no usernames, no nothing."

Tinfoil won't save you this time.