Unless you've been locked away in an isolated Montana cabin for the last few years, you'll have noticed that radio frequency allocations are serious business. A few kilohertz here or a few megahertz there can cost billions of dollars to acquire, make or break a mobile carrier, or render the Global Positioning System -- and the US military's ability to use targeted munitions -- null and void. What you probably don't know, though, is why it's so hard to get your hands on a block of radio spectrum.