True: http://en.wikipedia.org/wiki/Percent-encoding#The_application.2Fx-www-form-urlencoded_type

So it comes down to what serialize and deserialize should do. I think "serialize into a query-compatible string" is the more common case. Serializing for a post body w/ x-www-* is not as common. We could have getXHR handle that portion as necessary. Thoughts?