Very good point, but computing devices don't have scaling problems that the other technologies you listed have. Nuclear would have had a similar generality if,

Very good point, but computing devices don't have scaling problems that the other technologies you listed have. Nuclear would have had a similar generality if, for example, you could safely run a fission power device on your phone, for example -- but you can't; it just didn't scale down at the required safety level. Similarly, air travel doesn't scale down as people thought it would (still no flying cars) even though it works very well on large scale (airlines, combined, have near monopoly on long-distance travel). Computing scales both up (supercomputers) and down (cell phones). It may be that current silicon chips won't scale down to cellular level, but it also may be that (a) such scaling is not required for human-level AI (I believe it isn't), or that (b) other technologies such as graphene may replace silicon.