I first referenced this study a few weeks ago.

The hottest growth area in the social sciences field is computational social science. This is often based on privileged access to electronic data sets such as e-mail records, mobile-phone call logs and web-search histories of millions of individuals.

Such studies are ushering in a revolution in the social sciences, specialists say. But there is a trade-off between the scientific interest in working with such data and concerns about privacy.

The research paper is "Structure and tie strengths in mobile communication networks".