Apologies for making my first post in such a contentious thread...I have a good deal of experience dealing with snakes. I agree that they shouldn't be killed indicriminately, but allowing poisonous snakes to hang around in areas where there are children would probably not be a great idea. Some non-poisonous snakes mimic their more dangerous relatives and are threatened or endangered and could cause considerable fines if killed even in states that don't protect all snakes (and you're caught heh heh).
Keep in mind that the toxicity of the venom of the pit vipers varies a great deal, the copperhead's venom is the least, followed by the cottonmouth, then the rattlesnakes. A copperhead bite on an extremity isn't extremely dangerous to a healthy adult, while an eastern diamondback bite to the torso can be life-threatening, and rapidly fatal to the sick, the elderly, or children. The wide variance in effects of bites by the same species is due to the fact that pit vipers have control of the amount of venom delivered in a bite; a warning bite may contain no venom, while a snake that has been poked at may envenomate massively. Their venom load may be also depleted by recent feeding episodes.
The cottonmouth really doesn't deserve the fearsome reputation, they are very hesitant to bite unless provoked. I have inadvertantly been within easy range of large ones that were content to scare me half to death and then turn and slither away as soon as they felt they had room. The threat display goes through three stages, rattling the tail in the leaves or water, the mouth display that gives them their name, and if cornered they will sometimes charge right at the threat with the head held very high. The charging behavior is mostly bluff, they will usually veer off right at the last second, but it is very unnerving to be ran at by large poisonous snakes, so most animals/people will give ground at this point. If they are coiled in a defensive posture, they will most definitely strike if harrassed, but given sufficient room they will try to escape. Attempting to kill one with a stick or similar will invite a defensive counter-attack, and this is where most bites happen.
Even though they are the least venomous, the copperheads are the most likely biters. They have a behavioral tendency to get still and hide if approached, and rely on their camo color pattern to blend in-if you're not looking close it's pretty easy to step on one, or put a hand on it. I was bitten on the finger by one of these some years ago, very painful, not recomended.
Snakes are deaf, but very sensitive to ground vibrations. If you're in snake country make your footfalls heavy, even stomping the ground occasionally, and they'll usually get out of your way. If you have time to draw and aim, you've got time to back up a few feet and go around, but I also wouldn't tolerate poisonous snakes in my yard. A .38/.357 revolver with rat shot is very efficient and little trouble to carry, with small ricochet/downrange problems.
