In a world with increased bandwidth everywhere, what if our many laptop computers, which are expensive and easily damaged, were replaced with portable terminals that had only a display, keyboard, and wireless connection?
Your terminal would connect to the internet, hook back to your main PC, which you would then operate from afar...wirelessly! It would have only a bare minimum of CPU and memory, and would be useful only for such connections, but could connect from any internet connection, wired or wireless, and it it broke, it would be cheap to replace.
It would by necessity be more complex than a traditional TTY terminal, due to needing to do TCP/IP, and either a forwarding protocol like Go2mypc for Windows users, or X-Forwarding for UNIX ones, but beyond that it would shift almost all the computation expense to the desktop machine, that was sitting idle in the first place. Depending on how it works, it may be extremely cheap, due to specialized and easy to manufacture chips.
On the downside of this, it would use a lot of bandwidth, and may require encryption lest someone snoop the traffic to learn people's passwords and finances. Configuration would confuse the average user. I can easily imagine rent-a-machine services renting CPU cycles to this kind of machine, too.
I can also imagine it cheapening the perceived value of computers. Game go badly? Smash your terminal with a baseball bat. Wife's mad that you're doing spreadsheets instead of taking out the trash? Into the pool it goes. I can imagine at some point the main desktop machine gets trashed instead and I wind up with a "It cost how much now?!?!?!?!" call.
Also, since it'll need independent CPU and memory to even handle a TCP/IP connection with encryption, it probably won't be cheaper than existing netbooks. ...damnit.