I loathe Facebook. I could think of nothing worse than having Facebook strapped to my face and it's never going to happen for me.
The problem for Mark is, anything he innovates will be pretty easy to steal / copy and there will be a huge market for Apple (for example) to build something similar but more trustworthy for people to buy...this is all under the proviso that VR actually takes off. Personally, I'm not so sure it will because while I find it a fun novelty with some application, I feel there is too much value in being aware of my surroundings to go "all in".