Does anyone really think the MacBook is dinosaur sized?
Yes.
I have no desire, nor any need, to carry anything bigger than 10"-ish screen.
I have no need for my mobile device to have a full power CPU.
I do have a desire to keep my gadget bag small and light. I can easily carry a 8.9"/9" screen device in my smaller gadget bag. I can carry a 10" one in my larger gadget bag. I will not carry a bigger gadget bag, period. Nor will I carry a separate laptop bag. If Apple wants me to own a mobile Apple computer, it will have at least a 7"-ish screen (because smaller than that is too small) and no more than a 10"-ish screen. Nothing outside of that size range is acceptable for my dollars. (it also has to have a physical keyboard, at least as an external option; that's the other reason an iPhone/iPod-Touch aren't acceptable -- no current official (non-jailbroken) support for a physical keyboard)
What I want/care about is basically something for checking mail, reading RSS, light web surfing, and chatting while I'm on the bus/train or in a cafe. In a pinch, I might need to use SSH to reach my servers while I'm out and about, or manage their web interfaces. Maybe run a VNC viewer. Maybe read some PDFs/ebooks/documents. That's it.
All of that other stuff that a macbook as the power to do? _Worthless_ to me while I'm mobile. So, why pay extra for something that's too big and doesn't give me anything I want/need?
The thing that's really close to ideal for me ... I have a Samsung Q1 Ultra with Ubuntu-UMPC on it. The thumb keyboards are a little awkward ... more because they're 4 row instead of 5 row, and some of the keys are awkwardly placed. If it had OS X and an iPhone-like Front Row overlay UI, Apple aesthetics, better OS/hw integration (a linux shortcoming), usable screen rotation, usable portrait mode virtual keyboard*, a translucent split-thumb virtual keyboard for landscape mode, some form of WWAN support, and otherwise had similar peripheral support and size as the Q1 Ultra (requiring a dock or not) ... it would be great. Bonus points for an attachable keyboard (like the Touch Book).
If it was a 10" screen, with no keypads/mouse-stick/dpad, instead of the Q1 Ultra's 7" screen ... then I'd probably be ok with that. 10" screen, very wide aspect ratio (more than 16x9), iPhone type styling, attachable keyboard, and the above features ... that'd be hard for me to pass up. Even if it was more than $900.
(* a usable app in the top half of the screen, a usable virtual thumb keyboard in the bottom half; so, full 80x24 SSH + keyboard for example)