"I think there is a world market for maybe five computers." – Thomas Watson, chairman of IBM, 1943.
With hindsight he probably meant Google-like mega data centres of which I think there are only a few world-wide.

"640KB ought to be enough for anybody." – Bill Gates, 1981.
His company became the main cause of bloatware. If CPU instruction sets were of a high-enough order and most data-processing was done at a mega data centre your handheld device might only need 640KB or so of local cache memory.

"There is no reason anyone would want a computer in their home." – Ken Olson, president, chairman and founder of Digital Equipment Corp.,1977.
No hard-to-setup and use computer system at my place please. I want to be educated and entertained and to be able to communicate richly. Give me an appliance no more complicated than a 'phone or a TV/PVR and I want one that does what I want not what I say or do.