Top NYC office landlord Vornado, which just inked a huge deal with Facebook, is deploying facial-recognition tech across its entire portfolio. Here's how it works and what happens with the data.

· Vornado Realty Trust began installing facial recognition systems in buildings it owns in New York City five years ago. 
· The company, one of the city's largest commercial landlords with 19 million square feet across 35 buildings, recently expanded its use of the tech to 11 buildings and plans to roll it out across its...