"By updating its API to support posting, users of clients and plugins would start to actively publish to Google+. This would quickly increase the amount and quality of content available on this platform and in turn attract users and engagement."
No, it wouldn't. It would turn into Facebook, which right now is a stream of unreleated, unuseful junk. Why do I care if my friends on the other side of the state check into a bar? I don't. It's pointless, useless information.
What Facebook has built is a data dumping ground, songs listened to, bars checked into, and the always obnoxious comment from someone you know to someone you don't.
What G+ has tried to do, at least with games, is contextualize the notifications. If I'm playing a game, then I see the game notifications. They never appear in the main stream. I like this. I really hate the Spotify track notifications in Facebook, they're awful. I'm perfectly fine with seeing them in Spotify, because I've already made a decision to listen to music.
Facebook opened up the flood gates, and everyone is drowning. Google is taking the opposite approach, but everyone is thirsty. It seems a lot easier for Google to move towards more useful notifications than for Facebook to back away from them.