If you look at the FCC frequency allocations chart (warning: PDF), you'll notice how many different industries and applications that are trying to use the wireless spectrum. And this chart is deceiving because much of the spectrum isn't usable for modern applications. Lower frequencies don't provide enough bandwidth, and high frequencies require very rare materials for the electronic components, so they are too expensive for most purposes.
There has been an explosion in research for wireless communication over the last several years because the demand for more capabilities has increased. This has led to incredibly complex encoding schemes and manipulation of the physical radio waves, and is now leading into cognitive radio.
The sad part is that most of the usable spectrum, even though allocated, remains underutilized. I am a researcher studying the spectral usage in Chicago, and we have calculated that the most heavily used parts of the spectrum are still only occupied about 11% of the time. There are also many parts of the spectrum that have been allocated, but are only used in certain geographical locations. The big TV Whitespace movement promises to introduce technologies that can potentially help us better utilize unused parts of the spectrum where available.
Am I surprised that the cellphone carriers paid $20 billion for the license? No. The survival of their company depends on them being able to transmit wireless signals. Just like an airline has to pay fees at an airport in order to be able to land their planes. There is no other option.