What kind of projections Youtube and Facebook use for VR?

They are both using H.264 video coding standard and MP4 container [1]. But, they have different projections:

Facebook is using the cubemap projection [2].
Youtube is using equirectangular projection [3].


References
[1] Qian, Feng, et al. "Optimizing 360 video delivery over cellular networks." Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges. ACM, 2016.
[2] Under the hood: Building 360 video. https://code.facebook.com/posts/1638767863078802.
[3] YouTube live in 360 degrees encoder settings. https://support.google.com/youtube/answer/6396222.

VR Forcast

Virtual Reality (VR) technology is projected to form a big market of $120 billion by 2020 [1].


References
[1] Augmented/Virtual Reality revenue forecast revised to hit $120 billion by 2020. http://goo.gl/Lxf4Sy.