Technology alone cannot make a revolution. The other facet of taking technology to be independent of the social context within which it always already operates is to misjudge its possible, practicable alliances and uses. The bad guys always have the newest, bestest, fastest, powerfulest stuff, and they always have more of it than anyone else. And even when things are more even, any tool can be used to impede social change as well as to foster it. Hence, even if XML had some property especially conducive of citizen empowerment, the forces that oppose such empowerment are free to use it too.
Technology often amounts to a draw in social struggle.
Most enthusiastic proponents of XML have the cart before the horse or, to mix metaphors, they have the tail, XML, wagging the dog, society and social possibility.