Oh, I misread the code. Having a default querystring parameter name of `callback` makes sense to me.  That's what jQuery uses as well.  Perhaps the name of `_callback` needs to be different to better describe that.  Perhaps `_callbackParam` or `_callbackArg` or `_jsonpCallback`?  In any case I'm not for removing a simple way to enable jsonp that uses a default that jQuery also uses.