What do you think communicating is, if not the sharing and exchanging of data?
In the point I was trying to make, it doesn't matter what I think it is. It is what does the average FB user think it is? And rightly or wrongly, I don't think those users consider their interactions with other FB users to be "data". Even worse, I suspect most have some vague notion that their "private" conversations are actually private. They probably set up permissions on who could see their profile, posts, photos and other information - which would cause them to labor under that delusion.