"Additionally, the datacenter 365 Main -- which hosts Web sites including Craigslist and Yelp -- lost power."

Holy COW. 365 Main is a top-tier datacenter; it was built for the guvmint, who then never moved in. They've got huge flywheels on the roof for power interruptions. The whole building is on rollers, and can move a half a meter any horizontal dimension. Of all the datacenters in SF, I'm surprised that they had problems. On the other hand, when I was a customer there, I don't recall ever getting any notifications that they were testing the offline power systems, which is something I did get regularly at Navisite, in a different building.