From an article in the New York Times:

The security flaws Mr. Kean’s team is scrambling to catch and patch are part of the larger problem with software today. The programs that people rely on for all manner of tasks — from writing reports and sending e-mail, to monitoring factory floors and managing electric power grids — are becoming increasingly large, complex and, all but inevitably, filled with bugs.

I just don’t agree about the inevitability of it, software is filled with bugs because people like it that way. I’m serious. If people wanted software that was virtually bug free they could have it. Right now. It’s a matter of cost though. In real mission critical systems (e.g. flight computers, life support systems, the controls for nuclear reactors, etc.) I would expect to find a very low level of bugs. I’d also expect to have to pay somewhat more than $500 for it.