A bit of a coincidence recently to witness a slew of recent outages/scalability issues on high profile sites. First it was the well-publicized Amazon outage, followed by Mozilla's Outage on Firefox 3 Launch Day, Google Apps outage and now Facebook's logged-in HomePage:
One of the publicized outages from last year was due to a site update. This spotted the last hour (perhaps a lot earlier than this) and the root cause release should be interesting.