Researchers at Carnegie Mellon University in Pittsburgh have developed different forms of facial recognition technology to highlight the positives and negatives of a world without anonymity.

Alessandro Acquisti, an associate professor of information technology and public policy, created an experimental smart phone application that is capable of snapping a photograph of a stranger's face in order to produce that individual's social security number.

The technology matches photographs taken with smart phones with those on Facebook.

Across campus, students at the CyLab Biometrics Centre are developing facial recognition hardware and software to assist police and military in identifying criminals.

Produced by the BBC's Matt Danzico