I for one respect Asimov's analogy, even though it may be a bit over-simplified. Actually, they are not equivalent at all. There was never any scientific law to which anyone was ever able to point which led to claims that we'd never exceed the speed of sound. We see here another example of the public confusing technology with science. No advance in technology will ever let us step off the edge of the flat earth, or violate other basic physical laws.
Nature is very unforgiving that way.
And I hasten to point out that, unlike meteors, which routinely go faster than sound, we have not one shred of verifiable evidence that anything has ever gone faster than light, in nature or otherwise. So much for FTL travel . Similar arguments apply, but he bottom line is, even if I'm wrong about this, microwave and optical SETI still make good sense. Imagine that there is a continuum of technological development, somewhere on which each of the multitudes of probable civilizations will fall. They are not all at the same level of development, because they are neither all the same age, nor evolutionarily homogeneous.