[potlatch]

Doesn't sound like a two legged thing would give accuracy to a gun resting on it. I'm a woman who'se never hunted, so I'm not familiar with this stuff.

[TheLion]

The third leg, so to speak, would be the shoulder or hand that is firing. That provides the balance. From what I have seen, the legs are only about a foot in length. They may be adjustible? Maybe someone here knows. Some of the threads on the snipers weapon have pictures.

[BlueDragon]

Bi-pods are used by some, but rarely. They are used (if at all) most often, around my locale, by the cattlemen shooting ground squirrels. The squirrels make a very small target, and one needs to stay back aways (like 100-200 yrds) for the little critters to feel safe enough to come out of their holes and run around.
Most all bipods are fairly short legged, which require for their use, the rifleman to either lay prone on the ground, or use a stationary object as a rest. All of the above can equate with greater accuracy, which is why the varmit shooters pay the extra dollars, and expend the extra effort and hassle to use a bi-pod. Otherwise, the common military uses have been mentioned by others on this thread, already. All in all, the ground squirrels seem to be fairly well holding their own, in this one-sided, small arms conflict.