You got it right!! Social media... but
What is not well known by most Facebook users is its involvement in the hardware manufacture and the desire to whitebox all its equipment ie, it wants all or most part of its hardware to be run on Open Source hardware, not proprietary hardware like Cisco etc.
This saw Facebook joining hands with other organisations and contribute to the OCP(Open Computer Project). Being a member, Facebook lived by its promise and contributed in the manufacturing of fast switch which they used to replace everything in there datacentre.
Whilst you are enjoying clicking likes on FB, the data you are producing is now being handled by whiteboxed purpose built switches inside FB datacentres
But Facebook have decided to go further! They now want to challenge the telco hardware industry and start to manufacture the fibre switches and relevant equipment. This is perfectly understandable if you look the aggressive nature FB is taking towards OTT development. If telcos do not want to play ball, FB is ready to go it alone.
But to do so at a lower cost which will not affect its users, it will need to acquire cheaper hardware for infrastructure building, and branded hardware do not come cheap.
I recently wanted to acquire a Cisco 6807 core switch for a potential project. That unit with just single supervisor engine and 48 10G spf+ ports is a cool $130 000
Now imagine FB trying to by edge routers, core switches and aggregation routers, that will be a massive bill.