They aren't necessary, but they sure are nice to have! A good set of front shocks will drastically reduce the abuse your arms will take, and a good rear shock will keep your butt from getting too saddle sore. I'd say the rear shock is not quite as important as the front because you're usually standing up off the seat while riding in the really rough stuff anyway.

It depends on how extreme you want to go. Agressive Downhill /Freeride requires it .Those bikes are upwards of one grand though and the rides not for the meek. For most recreational riders a 'rigid' (no suspension) to a 'hardtail' (front suspension only) would be just fine .

In general, shocks give greater control and allow higher speeds, negotiation of larger obstacles, and greater comfort. The downside is that many shocks produce 'bob': a loss of power as some of the pedalling energy is absorbed by the movement of the shock. Also, the shock makes the bike slightly heavier. The type of shock, and the geometry of the travel determine the extent to which the advantages and disadvantages are felt, and different setups are used for different types of riding. Also, there is rear suspension and front suspension, and the advantages of each can be thought of seperately. Full suspension bikes (shocks front and rear) are now dominant in all areas of mountain bike racing where any type of distance is covered - cross country, freeride, downhill. Hardtails (bikes with no rear shocks) are currently dominant in jumping, dual slalom and trials, as these sports require very short sharp bursts of power, and tight control, without worrying too much about the surface being ridden over - much like BMX. The full-suss trend began in the downhill sector, and these days every downhill bike has suspension. The same is pretty much true for freeride, which has similar requirements, plus the need to go uphill! Full suspension in cross-country is still the subject of some debate, and many top riders still ride and win on hardtails, although very few people these days would deny the effectiveness of full suspension in XC, and many staunch hardtailers have been swung by recent innovations in full suspension designs. Cheap full suspension bikes are bad almost without exception because cheap shocks bob more and rebound less effectively and many cheaper bikes have bad geometry. Budget buyers would do well to stick to hardtails. So is rear suspension necessary? No, not really - but it comes highly recommended. As for front suspension, it's pretty much standard on all mountain bikes, and while it is not totally necessary (early bikes didn't have it and were still pretty fun) it should be considered as important as having gears. Suspension, front or rear provides far superior control, increased speed, enhanced safety, allows negotiation of bigger obstacles, produces less fatigue (particularly to the arms, knees and wrists), and gives less chance of injury.

When on fire trails you should have at least front shocks and you don't really need back shocks. but once I did some trails in colorado and i was glad i had full suspension.

my buddy rides what is called a single speed rigid.one gear,zero suspension.it's a blast not for noobs.you must have some talent and bike handling skills.

NO! At least not for cross country. I have 2 bikes, one hard tail with rigid forks, the other full suspension. Unless you are hard hitting rough trails, chances are the inefficiencies and greater weight of the suspension will slow you down. Most of my riding is on the rigid bike which is so light you can simply 'glide' over the rough stuff. Sure it can take a little more skill, but with a little bit of practice the rigid bike is a much more satisfying ride. Having said that, I'll switch to my full suspension for down hill mountain tracks.