Being the radio geek that I seem to be becoming, I guess I'll take a stab at this one. Keep in mind, a grain of salt should go with everything hereafter. I may have picked up my HAM license, and been addicted to this junk for a while, but I'm still very much a novice in the radio-comm world.
That said, I see two real options when it comes to general backcountry radio use. GMRS, and ham radio, with my personal preference wanting to lean towards ham, but reality kinda gets in the way of that wish.
This is what you'll find in pretty much every bubble pack radio at Walmart, Costco, etc. For the most part, they're all the same. 22 channels (1-14 are 'FRS', while 1-7 and 15-22 are 'GMRS' (note the overlap of 1-7,)) short, permananent antennas, and often feature rich with extras like weather radio, built in flashlights, nity beeping doodads, etc. One thing worth noting is that these radios REQUIRE AN FCC-GRANTED LICENSE if you plan to use anything except channels 8-14 which are strictly FRS. GMRS is the part that requires the license. Also worth noting is that pretty much NOBODY actually follows that rule. While I certainly can't condone ignoring the law on this one on a public forum, let's just say that it's more common then jaywalking, and outside of businesses using the frequencies, about as consequence-free.
All in all, these radios are great for short range communication in the 2-mile-or-so range. They all advertise MUCH higher numbers. A pair I saw at Costco yesterday are rated at 35 miles (nice radios actually.) That number always comes from truly ideal conditions that nobody is gonna find in their actual use. Generally it means they took a radio, put it on top of a tall mountain right next to a large body of water, and sent the other radio out onto the water in a boat while maintaining direct line of sight. In the real world, 2 miles is a pretty safe bet most of the time, and sometimes more or less depending on the terrain or other conditions. I've seen some of those radios push the 5 mile envelope in mostly flat areas, but I wouldn't wanna bank on them.
GMRS radios are, however, EXTREMELY common. Everyone has one (or more) laying around and they're easy acquire and use. This whole search for Joe thing got me thinking recently, and I think it would be a good thing if the hiking community settled on one of the channels in the 22-channel range to be some sort of unofficial 'hiker' channel. Great for emergency use, or just to shout out and see if you're really alone out there =) That said, I'm pretty a few National Parks actually monitor channel 1 these days.
There's SO much to cover on this one, but the short version is that anything GMRS can do, ham can do better, and ham can do a lot that gmrs can't even dream of.
First off, let's get this out of the way. It requires a license. And not "requires" in quotes, but you really do need a license, or trust me, you WILL be caught using any of the ham frequencies without it. Suffice it to say the FCC takes enforcement seriously, and the ham community takes it even moreso. THe good news is, it's truly not hard to get. It looks daunting at first, but just remember that there are grade-school kids who hold the top license ("extra" class) out there, so any average Joe who spends a little time studying can easily get the entry-level license ("technician" class.) If anyone is interested, I can certainly post up some more info on that task. Some free websites, plus a $20 or so study guide, and it's a breeze. The license itself is also technically free. You just end up paying about $15 to the volunteer exam coordinator for administering the test. I studied for less than a week proper, and in one afternoon was able to sit in on a cram session run by the MCSO Communications Posse and pass my Tech test that day. Only 35 questions, multiple choice, and the ACTUAL questions AND answers are published and freely available. =)
Ok, thats the annoying part that turns most people off of ham. Now for the good part... What IS it, and what can it do?
Ham isn't really anything special. Just like any other 2-way radio, it takes your voice, modulates it, slaps it onto a frequency, and transmits it out via nifty radio waves. GMRS radios spit out your voice, via Frequency Modulation, on frequencies around 462 mhz, and you get (on most radios) 22 channels (or frequencies) to choose from. Ham just gives you a *LOT* more. While GMRS/FRS radios just give you those 22 pre-defined slots to transmit on, ham gives you massive ranges you can use. One small example would be the "2 meter band" (techie term) that lets you use frequencies from 144mhz to 148mhz. When you consider that the frequencies are in steps as small as 144.005, 144.010, 144.015... and so on, you can see how the horizons just open up. And that's just a small portion of what the ENTRY level license gets ya.
The equipment itself isn't anything too special either. They're just like your typical Motorola Talkabout bubble pack radio, but with a lot more frequencies, ability to use different antennas, more transmit power, etc. (GMRS tends to stop at 2 watts, whereas the average ham handheld can push out 5 watts.) The ability to use different antennas also makes a WORLD of difference... far more than additional wattage. Slapping on a $30 antenna can really give you some crazy range. For example, when sitting on top of Mt. Peely a couple weeks ago I was able to connect to a repeater that was located on the Chase bank tower in downtown Phoenix, and make a phone call through it. I was also able to contact one repeater on Mt. Ord, Thompson Peak, the White Tanks, Mesa, Shaw Butte, MT. LEMMON, and even Mt Elden. Being a hiking community, I'm sure you guys know just how far those peaks really are. =)
Another huge bonus to ham radio is REPEATERS. These are FREE systems that sit atop almost every major mountain in Arizona and usually have much larger antennas (measured in yards, not inches) and much more power. You transmit to that repeater, and it re-broadcasts your message to it's radius. Just to give you an idea of what some repeaters can get as far as coverage...http://k5ehx.net/repeaters/qrepeater.php?id=342
You can be anywhere within the range of that repeater, and if you can hit it, you can talk to any other radio in that same radius. Heck, there's one repeater in Tucson on Mt. Lemmon that I was able to hit from my 3rd story bedroom in NE Phoenix with just a 5 watt handheld, 17in antenna, and too much spare time =)
Yet another nice bonus is that many repeaters have what's called an 'autopatch'. This is a device on the repeater itself that lets you make phone calls with your radio. You press the push to talk button, key in some codes, and bada bing, you are making someone's phone ring and you've got a phone call. Ever wanna order pizza from the top of a mountain? muahahahahh! Seriously though, this could be a huge safety feature for hikers. I was making phone calls on Mt. Peely in a spot where I couldn't even get SMS messages to go out. Throughout pretty much all of the path from trailhead to the top I had communication with a repeater sitting atop Mt. Ord, crystal clear.
I should also add that these little radios can do a lot of other things like listen to weather radio, listen to GMRS/FRS, listen to CB, listen to public services (Phoenix Fire and DPS are two that I listen to often,) listen to aircraft, boats, shortwave radio from around the world, and so much more. In an emergency (and only then) if a radio has been tweaked a little bit, it can even transmit to the above. God knows I hope to never test it, but it would not be hard for me to talk to an airplane flying overhead if I needed help. I was even able to listen to the radio chatter from the official SAR teams on the first weekend (the one where we all got shut out of the road to the trailhead by MCSO.)
Lastly, different frequency ranges tend to behave differently in the wild. Generally, the lower the frequency, the better it works for wilderness use. That's why you'll see most S&R groups sticking to frequencies in the 140mhz area (which is an area of the radio spectrum that ham radio users get to use as well.) You can go lower, but at a certain point you need antennas that are just not feasible for handheld use for them to be really effective.
I'm certain that I'm missing some things here, but this should give a pretty basic idea of where my thoughts are on this one. Ham takes some effort, but it can pay off many times over. Of course, some (most) folks will simply never want to go that route. For those instances, pretty much any recent Motorola GMRS/FRS radio is going to be as good as it gets without ham. (I'm partial to just getting whatever Costco has for sale at the time. Good price, all the accessories, and of course a top notch satisfaction guarantee!)
Hopefully I didn't ramble too long that I bored folks. Either way, feel free to ask questions. If I can, I'll certainly answer them, or try to find our what I can't =)
For the record, I primarily carry my Yaesu VX-7R these days (although MUCH less-pricey options definitely do exist):http://www.hamradio.com/detail.cfm?pid=H0-006327
Once such less-pricey radio might be:http://www.hamradio.com/detail.cfm?pid=H0-010075
And this is actually a REMARKABLY feature-rich and capable radio for $80. In a lot of ways, it's just as good as that $300+ radio:http://shop.murs-radio.com/Puxing-PX-77 ... 77PLUS.htm
And I've also got probably a half dozen Motorola FRS/GMRS radios of various models (mostly from Costco), a couple Uniden GMRS/FRS radios, and a Cobra Marine VHF radio that also does GMRS.
Variety is the spice of life
PPS: I should mention that from my 3rd floor bedroom near Scottsdale/101 I was able to talk directly with a friend who lives on the south east side of the 101/60. 19 miles with handheld radios. =)