"With the advent of what is called "large scale integration" (being a term from the computer field, its acronym LSI is better known!) it seems to become technically feasible to build machines more like "clouds of arithmetic units" with information processing activities going on simultaneously all over the place, for shorter periods of time even independently of each other. Programming for such machines will pose completely different trade-off problems: one will be willing to invest in potentially useful computing activity before its actual usefulness has been established, all for the sake of speeding up the whole computation. But although I know such machines may be coming, I shall not touch these problems for the following reasons. First, as far as general purpose applications are concerned, I have my doubts about the effectiveness with which such forms of parallelism can ever be exploited. Second —and that is the most important consideration— parallel programming is an order of magnitude more difficult than sequential programming."
Also, the first mention of "cloud", although with a different meaning.