UPDATE: It appears that the Japanese government is taking the matter seriously and one hopes that given the intense scrutiny that this event is getting around the world that the information is accurate.
Meanwhile, it is likely that many groups will work hard to force intensive reviews of both Japanese boiling water reactor designs and the largely identical GE mark 1 design commonly used in the US in the 1960s and 1970s with the goal of delaying the building of new nuclear power plants until the reasons for the Japanese failure are understood. This is all very unfortunate for those looking for ways to decrease our dependence on foreign oil. The Japanese have known from day one that they are building nuclear power plants in earthquake-prone areas. An early report attributes at least one of the failures to having only three hours of battery backup in case the backup power supply is also knocked offline by an earthquake. Apparently, even though the nuclear power plant can generate its own steam even if it is turned off (because of the remaining radioactivity of the core), it was not designed to charge its own batteries.
Update: A second outer containment vessel has exploded. The Swiss government has also put a stop to all nuclear plant permit approvals pending a full investigation. The German government has ordered its similar reactors to be taken off line.
The best current explanation regarding the relative levels of radiation can be found in these New York Times articles:
UPDATE: June 6, 2011: Japan’s Nuclear Emergency Response Headquarters has issued a new evaluation on this date stating that Reactors 1, 2 and 3 experienced full 100% meltdown. There are also reports that radioactive emissions were twice what was announced. CNN