JSON wird jetzt von Google Base, Blogger, und Calendar unterstützt. Hilfe gibts in der Dokumentation, den Beispielen und dem GData blog:

„For those of you who have been trying to build client-side GData mashups but have been thwarted by the same-origin policy, we have some good news for you: you can now get public Base, Blogger, and Calendar feeds as JSON! This means that you can start displaying GData in your web page with a little JavaScript.“

Quelle: JSON in GData