This is great for small, cheap, independent inventors, who can't
afford to buy expensive machines for prototyping.

I've got a friend who does this. He builds models on the computer and a printer prints them in wax. then he makes molds and makes metal parts or something. I don't recall the exact process, but it's cool. they can make customized patrissimo bobble head dolls

That's awesome. Thanks for the link.

That is pretty damn cool.

When I was at Brandeis one of our labs did computer-designed rapid prototyping of simple robots, and the sortware indicated where motors were to be added by the user after printing. It seems like this service might allow much better leeway with the greater variety of more robust materials they offer...

Check out ExpressPCB. They do the same thing for circuit boards, and you get a much better product than if you tried to make your own boards using tape and etching solution.