I did some looking around about the lightsquared issue last week, and the more I read about it, the more obvious it was never going to happen.

For those who hadn't seen many details (most news articles didn't have the relevant facts), I'll summarize.

Lightsquared bought a chunk of spectrum from a 3rd party that was intended for satellite to earth transmission(licensed as such, ie that was the only permitted use for that spectrum). They then wanted to use it for terrestrial transmission. The FCC said, we will allow you to do this, IF and ONLY IF you can prove there will be no interference to any GPS devices. Which they obviously haven't been able to do, which is why they're proposal is being rejected.

As for the specifics, anybody who isn't familiar with electronics design, basically it comes down to the filters used to listen to a specific part of the rf spectrum. Its impossible to listen to only an exact chunk of spectrum, without hearing anything on the other sides. Filters have a rolloff on either side where the amount of signal passed through approaches zero. Same thing with regards to transmission, you're going to bleed slightly beyond your spectrum. This is the reason that satellite spectrum ranges are contiguous, without terrestrial transmissions right next to them. The power used by terrestrial transmission is (if I remember right) somewhere around a billion times more powerful than that of satellite to earth transmission. It isn't practical to use the type of filters necessary to filter this kind of noise (they'd be huge). Which is why the spectrum in question was never licensed for terrestrial transmission.