Privacy War – Shots Fired by Apple at WWDC (via XDA Forums):

In his talk, Apple VP Craig Federghi talked about how data is processed by Siri without compromising user privacy, on-device as much as possible. He specifically mentioned the lack of cloud-based mining (ahem, Google and Facebook), and how the processing is done on-device, with the data staying on-device. Queries made to their server (for real-time internet-based queries, for example) are kept anonymous, not tied to an Apple ID, and not shared with third parties (another dig at the near-constant data sharing by applications on the Android platform).