As I sit and see login.facebook.com return "connection reset" - blocking me from logging in so that I can ask a friend a question - I'm caused to reflect on some of the unpardonable sins of sites. The first, and greatest, sin imo is denying access, either through error, fault, or lack of availability. Facebook has been a notoriously unstable site, I've noticed, with 3rd party plugin apps failing all the time. This, however, seems to be the first time that their entire authentication system has failed.
From a security perspective, this gives me an interesting thought: though in the security triad (CIA for Confidentiality, Integrity, and Availability), it seems that availability is perhaps the most annoying attribute to lose. Confidentiality is probably the most costly to lose. And then there's integrity. It's annoying, but perhaps not overly costly (most of the time). Case in point, for the last few days Google Reader has had a tough time with updating the status of various folders. I'm guessing that they're having sort of sync issue across their highly scalable platform. Undoubtedly, some new code push has hosed up the integrity of the status of read messages. This is a minor annoyance that is easily ignored, though, unlike complete lack of availability.
I promised a quick rant, so will just leave it at that.