As has been pointed out elsewhere in this thread, geosync orbits are useful for communications satellites (comsats), but they’re not the only orbits one can put comsats in. Its just easier to do it that way currently. (I’ll explain a bit more in a sec.) There’s actually lots of comsats in geosync orbit which are not being utilized to their full capacity. Nearly anyone can rent time on them (it ain’t cheap, but if you can afford uplink equipment, you can afford to rent the air time), what’s happening is that people are slowly shifting a lot of ground-based communications to comsats because its easier (and faster) to put a bird into orbit than it is to run fiber cross country or cross planet. So like with the dot com explosion, people are rushing to put sats up so that they can sell air time on them because even a broadcast network won’t be able to use up all the bandwidth available on a bird, so the rest of the bandwidth can get rented out to someone else. Helps pay for the initial start up costs.
However, thanks to the advances in computer technology, it is now possible (though not necessarily cheap) to put up a flock of sats which pass the signals to one another and then down to an Earth station (or multiple earth stations). This is how the Iridium sat phones work (yes, they’re back in business). If someone in say, Africa, wants to call someone in Russia using an Iridium phone here’s what happens:
The call from the Iridium phone goes up to the nearest sat, gets handed from sat to sat until it reaches whichever sat happens to be closest to Iridium’s earth station (known in the industry as a “gateway”) from there it hits a landline and is then routed to the number in Russia being called.
If you’re making an Iridium to Iridium call from Africa to Russia, then the call gets bounced around until it hits the sat closest to the other Iridium phone, whereupon it gets sent to that phone.
The system’s not perfect, there’s almost always the possibility of a dropped call, and there’s a bit of a delay (the amount varies depending upon circumstances), but you get used to it and don’t even notice it after a while. Still, I imagine in the future it will be the way most systems are done. Its more flexible than a geosynch system (you can’t get a signal on the north slope of a mountain in Alaska, for example, with a geosynch system), and if a bird goes down, there’s one which can take its place in next to no time (two hours, max).
Finally, a number of years ago someone wrote up an article in Analog describing a method of geosynching a sat to the poles (don’t remember the details, but I know the guy took a patent out on the idea which should just be about ready to expire). This is probably more than anyone wanted to know, but I work in the industry and when I get a chance to babble about it, I usually do so.
