Computing devices tend to fit into one of these categories, based on the device's physical characteristics:
- Stuff that fits in your pocket (e.g. phone)
- Stuff that you can carry around comfortably (e.g. tablet)
- Stuff that you can carry around in a bag (e.g. laptop)
- Stuff that you can fit in a back seat (e.g. desktop)
- Stuff that requires a truck to move (e.g. rack of servers)
Devices should be optimized for their category. If you want something that will fit in your pocket, you want the best thing that will fit in your pocket, but not so small that you'll lose it. If you're going to carry around a laptop bag, you want the best laptop, but you don't want something so big that it's too heavy or so small that you might as well just use your phone.
I don't get some of these new devices, like the Dell Streak, that are just a little too big to fit in your pocket. I think the Nokia MIDs are there too. Once you move into category #2, you might as well make the most of it. I think netbooks are right in between 2 and 3. They could be carried by themselves, but they're awkward to use with one hand and you often have to bring a power brick along. That's why they're really only attractive from a price standpoint.
Of course that pricing thing plays a big role in decisions, too, which is a significant factor in there being such a broad spectrum within each category.