My problem with nano is the hype. Its big proponents were way way too optimistic in their prognogstications. I believe from long personal experience that they totally miss the difficulties separating theory and lab wonders from practical engineering. There could even be unexpected nanoscale phenomena that totally prohibit what Drexler would label classical nanotek. Stiction issues, thermodynamic effects, power sources, etc. He does address all of them in theory polemically (I've bought all his books) but polemics does not get real world HARDWARE built.

I agree with the common view that biotek will be our 1st nanotek. We are learning to engineer there. But before we get carried away let's remember that we can't even cure a simple virus and can't cure cancer at the cell level. We're not even close. Cancer engineering like fusion power is always only a few billion dollars and a few years away.

Besides the engineering physics barriers to nano, the biggest obstical in my opinion is the "assembler". That's the magical device that builds copies of whatever, completely in concert with billions of other assemblers such that a perfectly molecularly duplicated or uniquely constructed "whatever" results. The miracal machine.

Two problems here. 1st the easiest one to solve. Having all these nanoscale assemblers communicate with their bretherin in concert for purposeful action. We can't do this on a macro scale today with networks in a reliable fashion. Think of all the network enhineers (semi-human at least) working to keep say Sprint's communications networks functioning. These nets are much smaller in # nodes than an assembler net. And these nets have nice dedicated wires (fibers, etc) for communication. This is solvable, but not easily, cheaply and not soon.

The 2nd problem is tha autonomous purposeful activity and manoeverability of these assemblers. Despite the layman's perception driven by Hollywood, we can't even build a clumsy robot capable of 2D motions autonomously using the most sophisticated large scale computers we have. That is a formidable barrier to nanomiracles.

Look, we'll pick up some biotricks from cell interactions and learn how to engineer useful stuff with them but we can safely say that the kinda nanotek that proponents wax eloquent over is many decades awya...if ever in some cases. Nanotek is a bit like a cult. Useful for great sci-fi but not imminent an any serious fashion.

-philw (goodbye to utility fog & other technomyths)