I am not sure I agree with this. If your bank freezes your account based on suspicious activity, do you change banks, or are you (usually) thankful? If FB is
so important that it cannot even be unavailable for a few days - which BTW I find a bit hilarious, then you better be prepared to accept that it has to operate on a similar level of caution. It seems like on the one hand people want FB to be as dependable as a bank (after all, there is a phrase 'banking on it'), while they also don't want the level of precaution that a bank is usually expected to take.
Not that I actually care if FB is successful or not in their venture, and I will be very happy if they go the way of MySpace, but I don't agree with the human cost and PR impact you are talking about.