That would indeed be the most obvious way to go, it would also make the device more powerful down the road since the computing is done on a smartphone which only get faster and faster by the year.
I'd say the computing is done "in the cloud". Low power transmission to your phone, then to the google datacenter.
It seems cool from a technology point, but I'm not sure I want to trust Google (and thereby the US Government) my life. Or am I doing that already by using Google Search and GMail?
Yeah, we're all doing it already. At this point it's more about managing what I do online then it is about avoiding using the services.
Google Glass will be massively popular with the active crowd (kind of how the GoCam got its big break) - I would personally use it in place of recording videos with my phone! I would not wear it all the time though, that's ridiculous.
I am sure that that is going to be the product that actually takes off. Google Glass will probably fail (at least the first iteration) but give some data for the next attempt. Then when Apple comes out with iGlasses everyone can act impressed.