This isn't 100% accurate.
I have observed cases where the data.text value is returned as an Object. This happens to me when the POST to http://api.msappspace.com/proxy/relay.proxy?<blob of params> produces a 500 on MySpace's server, and the MySpace API incorrectly returns a funky error object in the text field.
When this happens, we see traffic on our servers, but the response HTML that we send up never actually makes it through the MySpace proxy.