There's revolution going on and it's headed straight for your desktop. It's the desktop manufacturing revolution and it promises to bring just as much upheaval as the Industrial Revolution and Information Age have wrought.
I'm very interested in this development. There's a lot of excitement in the blogosphere about the 3D printers that will enable every wanna-be backyard tinkerer and reality hacker to make their own machine tools. I'm much more interested in what military planners might call the "long poles in the tent," those resources and building blocks without which this maker revolution would be impossible. I'll use my imagination.
The 3D printers themselves. It's impossible to get this party started without these all-purpose design and fabrication devices. Where do you get them? Who's going to make them? Will established industries try to outlaw them or pay their captive lawmakers to tax and regulate them out of reach of your local hackerspace or resilient community? If they break, is someone in your neo-tribe qualified to repair them? The RepRap Project seems to have the inside track on solving this problem.
The raw materials. Where do we find the toner for these printers? Right now even the most advanced 3D printers can only handle plastic polymers and some metal. Making your own complex, precision-controlled devices will require feedstock that's a lot more diverse.
The minor components. This flows from the raw materials problem. If your printer relies on a high-temperature laser to solder elements together, can those minor components be manufactured in the same way as a bulkier item that requires only simple polymers? This is relevant for those tiny components that have very special structures or require rare earth elements.
Alloys and metallurgy. How will a 3D printer combine two or more materials in a way that's more efficient than modern smelting? This is relevant for manufacturing products that must perform in extreme conditions of temperature and atmospheric pressure to exacting tolerances (like aircraft engine parts).
We're just at the beginning of this adventure and I don't have the answers. Looking for those answers is what makes this so much fun.