I heard that line before but I didn't realize they had made it their mantra. I wonder if they realize how it rings to all the third party developers who are fighting a daily struggle against the notoriously fickle Facebook APIs.
Agile development is great, but Facebook is a mature product: I wish they would keep the breaking to internal test builds.
That's not to defend API breakages or incomplete documentation and the pain it causes developers -- I'm not directly involved, but I know that we're definitely trying to get that turned around and fix some of the issues with Facebook Platform.