> If you don't have control over the XML, obviously converting it to > JSON is not a valid alternative.
[Read: if you don't even have enough control over the XML generating routine to get a simple namespace in there for a mission-critical API, then it'd be strange if you could add all-new code on the server to retrieve and convert XML into JSON -- though admittedly there may be some good or emergency-hack cases where you could do the latter but not the former. Converting on the client side, IMO, is performance suicide and I think way beneath the YQL/JSONP alternative.]
