If you can come up with an objection, chances are other people can too; since nanotech researchers seem to disagree that there are severe problems, I would suggest looking for solutions to your problems, first thing.
For these particular objections..
- Supplying energy, in a solid fabricator assembly, can be done using torque, eg. on a rotating diamond rod, for the smallest scale tools. Diamond rods have sufficient tensile strength to withstand torques far above the actual power requirements of a nanofactory; indeed, well into "do this on a large scale and your device will vaporize" levels.
For large-scale power distribution, standard electrical supplies will work well enough.
- Building the first fabricator is going to be tricky. There are two saving graces here; first, it does not need to be anywhere near as large or complex as a commercially viable one; second, it may be possible to leverage existing nanomachines (eg. biology) in order to bootstrap (there have been some promising developments lately). However, if we did have to build it atom by atom using a scanning-tunnel microscope (or thereabouts), we
could; it'd just take a few years. Well, months now, since they've come up with a highly parallel STM variant for manufacturing purposes.
I can hardly see this not having a major impact on the economy, either. Nanofactories
will be able to self-replicate (or they'd be impossible to make in the first place), and even just allowing for the current range of "hard" products - structural material, computer chips, whole computers, solar panels, screens, buttons, etc. etc. etc. - it'll turn a lot of the manufacturing economy into something much more like software.
It might not literally turn the economy upside down, but it's going to increase development speed and hobbyist creativity something fierce, while dropping prices for many products tremendously. I, for one, will want an open-source laptop.
