For many people, Facebook is how they interact with the web. It's their primary portal for talking with their friends, sharing photos, sending messages, and catching up on news stories.
Calling it a "social network" is like calling Google only a search engine. It's way, way more. And this outage is completely unprecedented. Can you recall a previous time that Facebook has been down? I can't.
This has a major impact on a lot of sites, and there are millions of people that do care about Facebook.
It is worthy of a HN submission, although I personally care most about the postmortem to find out what went wrong.
Imagine how many people are locked out of thousands of websites where the only way to sign in and check your order or something is by using Facebook login, which is not working.
It will be interesting to read postmortem but as far as "is down" stories go, they should be just auto-deleted from HN
Maybe I'm jaded because I don't really "get" the whole social network phenomena, but honestly, who really cares anyway? Productivity will (briefly) go up; a few people dependant on FB SSO's wont be able to log into some other pointless services and the internet will continue to function.
I normally down vote people when they say "what does xyz have to do with HN?", but 3 submissions commenting on a procrastination portal being down is really scraping the barrel.
[edit]
I see the submissions have now been consolidated. That makes much more sense. Good work HN admins :)