A very simple reason is the difference in business model between an hardware company, and a ad-based web site. Everyone doubts a single company can sustain the

A very simple reason is the difference in business model between an hardware company, and a ad-based web site. Everyone doubts a single company can sustain the two in parallel. Occulus original vision is to focus on the hardware, sell it with a margin and keep improving at it ( and the software on top). And have an ecosystem of service providers using your device. Much like Apple. Facebook wants to create free services that gets as much information from their user as possible, and create new features ( or buy concurrents) only when they see them slip away. It's pretty easy to predict where the two won't match.