An estimated 50 million people in New York, Detroit, Toronto and Ottawa as well as other cities were saved from spread of W32/Blaster by a massive power blackout. O.K., that is rather facetious, but there have already been unfounded rumours that Blaster caused the blackouts, so why not consider the flip side? All those PC's deprived of power were certainly not spreading Blaster. This also injects some reality into the disaster "statistics" that are often quoted for viruses and worms. We have never seen thousands of people trudging home on foot, or sleeping in the streets, because of a virus. Viruses do frequently cause disruption and sometimes damage, so we need to protect against them, but keep things in perspective.
Microsoft has not claimed responsibility for the power outage.