Anyway, i did not find any strong recommendation not to use this default implementation, so people might use it without any limitations.
P.S. I created my own based on md5 hash, but i`m not ready to suggest it now:).
Regardless of possible better implementations, I believe there is a bug in the default implementation. If you have a method with only one object parameter, that parameter is never hashed, it's simply returned.
I've made my own key generator where I changed this: