If a product is free most likely you are the product. I don't know how exactly but I don't believe Musk is doing it just because of his big hearth.
Every single genius has their own agenda which will benefit them. But let's take it the brighter side that he'll actually help a lot of communities if he can create a free internet to the entire world.
But the collateral of it is, we're all interconnected and he will have the idea where everyone is sitting or walking, in short, he will have the access for everyone's location.