The Most Incorrect Assumptions In Computing?

Miss Muis writes "After reading once again that Moore's Law will become obsolete, I amused myself thinking back to all the predictions, absolutes and impossibles in computing that have been surpassed with ease. In the late 80s I remember it being a well regarded popular 'fact' that 100MHz was the absolute limit for the speed of a CPU. Not too many years later I remember much discussion about hard drives for personal computers being physically unable to go much higher than 1GB. Let's not forget "I think there is a world market for maybe five computers" from the chairman of IBM in 1943, and of course 'Apple is dying...' (for the past 25 years). What are your favorite beliefs-turned-on-their-heads in the history of computing?"