We've got a number of messages from Facebook developers in the Mashable inbox tonight, reporting downtime of the Facebook platform - apps weren't working for a number of hours, they say. At last check, however, everything seems to be up and running smoothly. Crisis over.
I would say, however, that there's a tendency to overreact to downtime, with a few developers wondering if they should be building on a platform that isn't guaranteed to be up 100% of the time.
But Facebook Developers actually have it pretty good: it's a free service that gives them access to millions of users. What's more, downtime has been common across all startups that are reaching scale: Flickr in the early days, Pownce, Digg, YouTube and many more. Downtime is a fact of life, and even when those periods are extensive - as in the case of Twitter - they seem to pull through without losing too many users along the way.