I don't know anything about this overall, but I have some interesting anecdotes that show the power of Facebook around the world.
I've done some pretty substantial traveling throughout Asia, and just about everyone with a smartphone that I've met also has a Facebook account (excluding China).
In Myanmar (aka Burma) the strict military government restricted internet usage until they turned over control of the government last year. Most people are (within the last 12-24 months) using the internet for the first time! Most have never used a computer, and they only know the internet from an (Android) smartphone. However, every single person who I talked to there who had a smartphone had a Facebook.
The one local I talked to most in depth about this had never used Google! He said he didn't know how to use Google, and he didn't think he needed it. I explained what Google can help with: searching for information, reading news, etc. He showed me that he read news and did searches for things all from within the Facebook app.
I saw similar usage of Facebook in other developing Asian countries (Nepal, Thailand, Indonesia), where people used Facebook as a kind of substitute for a web browser / search engine.
You and I would never think to use Facebook as our internet portal, but it seems to be a very sticky and powerful tool for many of those just coming online.