Facebook is encouraging people to create and consume more videos on it's site, and particularly within it's mobile apps. Possibly as a way of gaining greater expertise in tracking video usage and related fields, Facebook is partnering with the famous Nielsen company to help track users' TV show watching habits on mobile devices such as phones and tablets. TV advertising is an incredibly large business, just as online video advertising is, so this could be viewed as Facebook testing the waters and trying to gather data and expertise.
Facebook has an ambition to ultimately dominate all kinds of advertising, so this could be viewed as a major step forward for them. More and more people are watching TV online and on their mobile devices rather than through traditional cable or over the air networks, so this is likely to be very important for the future of media consumption.