> Not even security related. If I decide to move from rails to django, now I have to wonder if somebody out there decided to talk to my app using json instead o

> Not even security related. If I decide to move from rails to django, now I have to wonder if somebody out there decided to talk to my app using json instead of regular get/post, and deal with migrating/breaking that client. If you didn't publicly document the fact that you accept a particular format you have no obligation to continue supporting it. Your point about the XML stands though, that sucked!