I think Mark move was a very smart one, I basically only use Facebook for its groups and I only have two groups I frequent. Many people are like that...
I couldn't refrain myself to connect this statement with Mark's new years resolution to learn more about cryptocurrencies. They may be completely unrelated, but hey, I am free to assume that they are, right?
Maybe, but I think it's the logical move even if that's unrelated at all. And Facebook looked at its current data and found out that more people liking/commenting on each other than on pages they follow.
Or maybe they just want to check how meaningful/profitable this is?