It depends on whom you ask about "changing" grammar rules, but in general, rules tend to relax or to become more international-ized because of the World Wide Web. I don't recommend Strunk & White, but I like to follow Fowler's MODERN ENGLISH USAGE while keeping an eye on New MLA guidelines.

I still stand by my main tenet: rules that don't affect the MEANING or CLARITY of what's being written are optional. Decorative commas are optional. Commas that clear away ambiguity are essential. Therefore, if Jack's climbing on top of both Sam & Daniel, then YAY ORGY. But if he's climbing on top of Sam as Daniel obliviously takes sentry duty, YAY COMMA.