CMOS technology already deals with atomic layers (the oxide step) four atoms thick. And they would like to make it thinner if they could get the leakage currents low enough.

Nanotechnology in a very primitive form is here already.

The venture capitalists who see no future in it are blind to reality.

Nanotechnology is not a fad, but it's also not a panacaea. Nanotechnology has been oversold, but that doesn't mean there isn't something there. For a mostly skeptical look at the claims in Engines Of Creation and similar nanohype, see Geniebusters. He's got some weird ideas about "transhumanism", but scroll down halfway and start with the Introduction. (Search on "contents" to get to the right spot.)

A great article - thanks for the link.

I feel that in some way the ultimate barrier to the "grey goo" scenario is entropy.

I dont think that anyone will deny that creating a particular state of order from chaos requires a minimal theoretical amount of energy - known as entropy.

The trick is where this energy is going to come from and how efficient will this process be?

Temperature differences - these have a theoretical maximum as dictated by Carnot's formula.

Chemical potential energy - once again offering a theoretical maximum to be used in the transformation of matter from one form to another - I think that comes under Gibb's free energy if memory serves.

Nuclear energy - apart from somehow harnessing radioactive decay I cannot see how this will factor in.

Dont forget that the assemblers themselves are subject to the laws of entropy as well - what are the chances of them replicating errors in themselves and the consequences of such.

Either way my gut feeling is that these assemblers will require large amounts of energy, whether it be chemical or thermal in nature. That energy will be what keeps the genie in his bottle and the dreaded grey goo at bay.

Microbes are molecular replicators, and they seem to manage quite well, despite all those considerations. "Grey goo" is perhaps best conceptualized as runaway artificial life. It doesn't have to assimilate every last atom of the planet to be an apocalyptic threat, it just has to render the world unlivable for us.