We've always been subject to propaganda from state and private powers, but now it's faster, in some ways more subtle... and potentially easier to study and counteract, because of the kinds and amount of data which big social networking companies now own. The author argues for Facebook to become more involved in countering other countries' interference, which is an admirable goal, though difficult to see how that might work for a company which wants to be friendly with every country in the world.
And it raises another issue we should all be watching very carefully: every change Facebook makes to what we see in our feeds significantly impacts what our society talks about. In fact, Facebook's released studies of how it can change people's moods. So what's Facebook's (and other social networks') responsibilities to the rest of society, and how do we ensure they're not abusing their power?