There's no link, or elaborate essay on the matter, but despite working in the industry, knowing people that work for the company, and even talking to ex-founders about their new startups, I never got Facebook (or its popularity) until just now.

It is IRC for a population that can't do IRC (and has likely never even heard of it).

That is what Facebook did differently than Myspace, Friendster, et al. If you want to try a startup in that market, I suspect this is the key: be a better async IRC than Facebook.

What's missing in Facebook's "IRC"? My first thought is bots, but I'm far from a normal user.

What are yours?