Reflecting upon Tim's pondering on computer screen size, the advancement in technology seems to be more evolutionary than revolutionary. Many new gadgets are developed to mimic the old ways how people used to solve problems, and a completely revolutionary approach of doing things is rare, and often being criticised as ahead of its time.
Take computer monitor aspect for instance, I think it is presented in the current 4:3 landscape form because it has always been this way - since the era of black and white TV screen. It was only 20 years ago, when the display units of most "personal computers" (Apple II, Commodore 64, Atari, etc) are your living room cathode-ray-tube TVs. Hence most software applications/computer games were designed to fit into this geometry. Throughout the years, the display technology advanced - from CGA to WUXGA, from CRT to LCD, from 13" monochrome to 21" in millions of colours - but most commercially successful display technology is just an evolution from yet another technology of the previous era - nothing extraordinary. Portrait-oriented monitor might have that wow-factor when you see one in the computer exhibition, but it is not an alternative, until you can easily buy one from your street-corner computer shop.
Why is that the case? I guess few people actually buy computers to read portrait A4/letter size pages. People want to use other applications, play games, watch movies, etc. TV is in landscape orientation because movies were in that format. So was the on-stage theatrical performance, where "movies" or "motion pictures" were evolved from.
Some paradigms are ageless. Let's talk about the ever-hyped pen computing and tablet technology. Instead of using a relatively revolutionary way of inputing data by taping on the keys, people now days want to go back to the old school way of jogging down ideas - by using a pen and a notebook without the ink. It might appeal to some as it is not much different than how they used to do things, but in reality, it sacrifices on both the performance a keyboard can give you (100WPM with stylus?) and convenience a pen+notepad can give you (battery, booting up, Windows crashing...)