If you're not one of the 172,000 Japanese people living within a dozen miles of the Fukushima Daiichi plant who have been advised (read: forced) to leave, you are breathing a sigh of relief while you hope things turn out okay.

But a new analysis carried out by Nature and the NASA Socioeconomic Data and Applications Center at Columbia University says two-thirds of the world’s 211 nuclear power plants have more people in the same radius than the ones who have had to flee their homes in Japan.  They're not all on known earthquake faults, obviously, but disaster concerns are an important public policy issue in times of disaster.

21 plants have populations larger than 1 million within a 30 KM radius, and 6 have more than 3 million within that radius.  KANUPP plant in Karachi, Pakistan has 8.2 million living within the radius.  In addition, 152 nuclear power plants have more than 1 million people living within 75 kilometers.
There's no objective metric for "danger" notes Science 2.0 fave Declan Butler at Nature, but population density certainly has to be a factor.

Here's a Google Map thing from Nature showing the location of the plants. It won't work with good browsers, like Opera. Sorry about that.

Obviously there is no reason for a panic.   The so-called "beyond design basis" events are not considered for each because we won't get a tsunami in Kansas but size is a factor.   The good news (well, bad for groups milking donations out of tragedy, like Greenpeace) is that age does not really seem to be a factor though the design certainly can be, with Chernobyl the example.  

Reactors, residents and risk - by Declan Butler at Nature