Saw a program on Discovery or Nat Geo about Rattlesnakes evolving quicker than biologists thought the way Evolution did. Because rattlers rattle people know they are there and kill them. Don't get me wrong, if they lived near me I would walk round with gun 24/7 and maybe start to keep a couple of Mongoose, maybe a honey badger (i digress a little), but this program showed events like the Annual Snake round up, 20,000 plus snakes a year rounded up in weekend in a single county. That puts an artificial skew on selection and the rattlers with a tendency not to rattle when disturbed are being un-naturally selected for. Footage showed a chap find a snake, provoke it and it just sat there, not until he started to lift it with a handling hook did it start to rattle.
Taking out the ones that slither into your yard won't upset the balance, but culling/decimating whole populations might not be the best idea if your intentions are to alleviate rattler problems, eventually the only rattlers could be the ones that don't rattle, and i know version I version i would rather live with (cos you ain't never going to get rid of them all)
So what i am trying to say from the comfort of the UK, is be careful, just because you can't hear a rattle, doesn't it isn't there any more