Big data analytics is their bread and butter – if they had a way to analyze Facebook messages for patterns and predictively useful metrics, I'm sure they would.
They are mostly about exploring the data yes, but they also do some data mining in the content in order to make connections. They attempt to pull out names and link them together and things along those lines.
I think they would be far more interested in mining all of the friendships to do the network analysis than the content of the chats.