A lot of people think they're okay because they aren't currently in pain or having numbness or carpal tunnel problems or whatever (BTW carpal tunnel is severely over-diagnosed and is also very easy to avoid; basically it's not a significant problem unless you are a retard and just mouse in a horrible position and ignore all the warning signs your body is sending you). In reality, all of these therapies can't really do much for you once you are in pain and having problems - the best time to work is *before* you have problems to prevent them.
Let me describe what happens to you when you sit at a computer day after day :
1. Your muscles just all generally atrophy because you're not doing a damn thing. Note that even if you work out this can be a big problem because you tend to only work your big movers, so you can get yourself into a dangerous situation where you have over-developed big movers and under-developed structural/stabilizer muscles.
2. Your hips lock up and your hamstrings shorten from sitting with knees bent all the time. Most of you actually sit on your low back, not your sit bones, which puts pressure on the vertebrae and nerves in the low back which can lead to sciatic pain and other nerve impingement disorders of the low body.
3. Your back rounds forward; obviously this happens badly if you slouch, but it also affects most people who try to be good and sit on a physioball or something, because they get tired and start resting on their arms and leaning into the monitor and keyboard. The back rounding forward does a lot of things - it shortens the muscles on the front of the body (mainly the pec minor) and it over-lengthens the muscles on the back (mainly the trapezies and teres major). Permanently stretched or compressed muscles are crippled - they can't execute their movement in their power zone near neutral. Back rounding also puts lots of bad pressure on the vertebrae, it pinches discs on the anterior side. Nerve bundles run out of your vertebrae through little holes and they get squeezed which leads to pain and weakness.
4. Your shoulders roll forward and get weak; partly because of #3. This is mainly because your arms are forward all the time, never above your head or even just relaxed at your side. The weight of your arms pulls the shoulder forward off where it should be resting. The shoulder is a very elaborate and delicate contraption - it doesn't have a ball and socket, the humerus just sort of sits up against the side of the body and is held in place by the rotator cuff tendon-muscular complex. By rolling the shoulder forward, parts of it are stretched and other compressed, which leads to weakness, constriction of nerves and blood flow, and pure mechanical disfunction (because it's in the wrong place, you can't get the right leverage with the right muscles and your body winds up compensating in bad ways).
Most people who have computer-related numbness or weakness or arm pain are actually have nerve pinching due to shoulder problems, not carpal tunnel. The nerve bundles from C5-C7 run through the shoulder and down the arm; they run through very small spaces which is fine if your body geometry is correct, but when you sit at a computer and your body gets all deformed with your head way forward and your upper back kyphotic and your shoulders rounded forward, it screws up the passages that the nerves should run through.
A lot of computer users think they are okay because they are working out or whatever. Certainly that is a good thing and a huge help, however you have to be very careful about how you do it and what you do.
There's a general societal problem that our image of the ideal male body right now is focused on abs and pecs. That leads people to over-develop the anterior muscles. This is like poison for computer user's bodies, because you are already rounded forward and the anterior muscles are over-shortened. Doing a bunch of crunches and bench presses will just make this work and do nothing to develop the stabilizers that you need. In fact this kind of training can make you even more primed for injury because you're moving heavy weights around and doing extreme athletic things without good stabilizers and basic body geometry.
BTW I love that Wikipedia has an entry for Tramp Stamp .