The new iPad

[gb2000ie]

In my opinion, Theory 2 is the main reason Siri is restricted to the iPhone 4s. Siri is just a software app, and would work just as well on the iPhone 4. But it's really the only sexy selling point Apple has to convince people to buy the upgraded model.

It's actually not "just a software app". The bit that runs on the phone is just a front-end. It just hears the sound and sends an encoded version of it off to Apple's servers to do the massive number crunching to figure out what you meant. The resources needed to do natural language recognition are signifficant, and the biggest problem with siri (other than lack of international support) is that the servers are often too busy and siri replies with an error message.

If they can't even cope with all the iPhone 4S users seamlessly yet, why would they make things worse? Betas are all about ironing things out, you keep the set of users small till you have it nailed down, then you open the floodgates. Clearly, siri is not ready to have the flood gates opened yet.

As for why it is absent from the iPad - I think your Theory 3 is a reasonable explanation. Also, the only microphone on the iPad is on the back and it's no where near as sophisticated as the iPhone mic. The tablet just isn't made for you to talk to it.

There's also no noise-cancelling mic on the iPad, making the task of understanding you MUCH harder.

B.