In some African countries, Facebook is free via Mobile Data (also Wikipedia).
Therefore, it becomes the "only" Internet.
They even have cases of piracy movies being shared/available within theses sites.
This is so prevalent that there are many study groups on facebook just because of that: it is the only place they can "freely" exchange ideas, and voluntaries from other countries (without these limitations) help by copying and pasting info and documents so others can 'freely' download it.
There are a ton. It's weird, because they use FB differently than a lot of people. It really is the 'internet'. Pirated movies and all.