When I write Clojure I tend not to worry too much about this. Most of my variable names will be declared with `let` and will have a very limited scope. I can go ahead and clash some builtin function name and not worry about it unless I happen to need that builtin function within the `let` block. It usually is the case that I don't need to.
Locally overriding builtin/global functions seems like a bug waiting to happen. There's no way to figure out if you actually intended to use the local variable inside of scope, or the function it overshadowed. It seems to me that in Lisp-1 all local variables should be prefixed with some sort of symbol so that they can never override globals.
