This is what Facebook has always failed at, but where MySpace succeeded. On MySpace, I became friends with and met some minor celebs; no such thing has ever happened on Facebook (except maybe in its very earliest days). Facebook has never been about new connections, or even reaching a new audience; it was designed start to finish as a way to broadcast to a network that you already have. Unless, of course, you're an advertiser.

Why wouldn't it be tractable with current AI? I'm assuming they have the brightest minds and some fairly hefty AI software constantly analyzing and running A/B experiments, the result being that the FB experience is gratifying, sticky or even addictive. Now, why not re-purpose some of those resources so that it becomes gratifying for people to expand out of their bubbles? The hardest thing about it is presumably that it doesn't contribute directly to the bottom line.