Perhaps something like what we have now. Each “printing station” would have several models. The most common model would be able to manufacture whole objects with a great variety, such as non-weapons and single-piece units that dispense food and clean water, clothing, etc. The next common model would be one that could download pre-made objects from a controlled network, available after availability with a license, and monitored knowingly like our telephone system is: each request is fed into a super-computer that monitors all activity, only notifying a real human being if something awry goes by. The third kind would be for scientists and publicly trustworthy individuals who not only have licenses for the technology (unpleasant as it may be– it irks my spirit to say it), but are under contract for specific use of the machine, that are completely programmable. These individuals would be responsible and liable for ALL the wares that would be manufactured by the generic, non-programmable machines. These people would be scanners and designers: that steak tasted great! Let’s destructively dis-assemble it and get that taste out there on the Internet! Or: this new device is self-protecting and capable of maintaining a minimal level of health in the human bloodstream– let’s make a machine that replicates them from the en mass nano-factories. BUT if those devices are able to be disassembled easily into dangerous components, or they release dangerous objects, they are as well as the criminals responsible for the deeds, and reprimanded.

I have also heard an idea that there could be a general nano-laboratory available to the general populace, but if its seal is breached, it will automatically destroy itself with acid, or something else more destructive, thereby destroying all nano-manipulation abilities.

Nobody Man

All large scale institutions, whether they be governmental or private, are bureaucracies. It is a law of nature that bureaucracy does not work. Any belief in centralized control of anything is really a belief in the efficacy of bureaucracy. Since this is definitionally impossible, any discussion of centralized control is definitionally meaningless drivel.

Also, bureaucracies are inherently parasitical.

Of course the future of nanotech (as well as the future of anything about human beings) is towards decentralization.