FB missed the boat on defining mobile platforms, they don't want to miss next potential platform, i.e. VR, AR and Mixed-Reality... goes back to their mission

To produce a wearable augmented reality device. Similar to google glass but more focused on personal experience and friends suggestions/likes. The like button is a very powerful tool. Another use could be to create a device that you wear and can visually transports you anywhere in the world, real time, so a you can sightsee or even visit with friends.

Entertainment - Gaming is source of revenue. Occulus Rift is an VR company. And gaming is going toward VR. - Occulus Rift is not the same as Google glass, it is more like Google Cardboard - so striffle competition Applications of VR; -Training e.g pilots use VR to train - The goal of facebook is to empower people to share and make the world more connected and open. VR allows you to be more connected. Image VR chatting. Imagine taking a tour in Italy using VR. They are also medical benifits of VR- for example people that are scared of heights can be cured of it by slowly exposing the to VR. But the main point is entertiament