The Facebook iOS app now has a menu item labelled "Protect" that installs a Facebook's own VPN app. This lets Facebook "protect" you by intercepting and spying on the traffic ofincluding your web browser.

So that's pretty sweet.

Facebook is pushing its data-tracking Onavo VPN within its main mobile app:

Instead, Onavo's VPN allow Facebook to monitor user activity across apps, giving Facebook a big advantage in terms of spotting new trends across the larger mobile ecosystem. For example, Facebook gets an early heads up about apps that are becoming breakout hits; it can tell which are seeing slowing user growth; it sees which apps' new features appear to be resonating with their users, and much more.

This data has already helped Facebook in a number of ways, most notably in its battle with Snapchat. At The WSJ reported last August, Facebook could tell that Instagram's launch of Stories -- a Snapchat-like feature -- was working to slow Snapchat's user growth, before the company itself even publicly disclosed this fact.