Why is Siri iPhone 4S only? Seems odd to me that the Siri assistant feature would be available only for the iPhone 4S. I have the Siri app (from the company Apple bought and integrated into the OS) running on my 3GS and it works just fine. So what gives? It surely isn't hardware. Then what? Just to move more 4S units?
It's supposed to use the phone's processor to do the voice recognition instead of sending the recording to the cloud to recognize as the Siri app does. This (apparently) requires the A5 processor.

It probably doesn't hurt, though, that it'll push 4S units.