Filepicker.io - File picker as a service.

FORBES: Y Combinator's Spring 2012 Demo Day: No Funding Talk In Pitches, But Plenty Of Funding Interest

To lead the project, Mr. Zuckerberg brought on an old Harvard friend, Sam Lessin, through the October 2010 acquisition of his file-sharing start-up, Drop-io.

WSJ: Facebook's New R&D Machine