You Are Who You Know

Intriguing paper with privacy implications:

You Are Who You Know:
Inferring User Profiles in Online Social Networks

In this paper, we ask the question: given attributes for
some fraction of the users in an online social network, can
we infer the attributes of the remaining users? In other
words, can the attributes of users, in combination with the
social network graph, be used to predict the attributes of
another user in the network? ... '
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