People are crafty. You dont have to have electricity at home to charge your phone. Its enough there is one power source in the village. (There was a news story about a boy that built a windmill, and the villagers paid him a bit to charge their phones). You dont even need your own phone. You can share or rent one by the minute.

Second hand smartphones are getting pretty cheap. 2.8 billion people live on less than 2 dollars a day. A second hand smart phone might go for 20 dollars. So its a few weeks worth of savings.

Imagine all those people getting on Facebook. They will find a way to use it for what they need.