...But most of it needs expensive equipment, fab facilities, testing systems etc.
You're forgetting that PC's were pretty expensive and had to be assembled and soldered together, just like the open source 3D printers today. Also, 3D printers becoming dramatically cheaper though some assembly is required for most of the open source designs.
If you think a group of disperse individuals will each have the same equipment to collaborate you're dreaming.
The RepRap community is a group of disperse individuals who have similar (3D printing) equipment and who are collaborating on making various designs, including the open source 3D printers themselves. You're right that it's not exactly common yet to download an (open source) object off Thingiverse.com and print it out. But right now thousands of RepRappers do this regularly. But the amount of people that operate RepRaps is doubling twice as fast as the transistors in Moore's Law (10 fold increases in 20 months). My research (did a big community survey with MIT) shows that there are modest differences between soft- and hardware sharing once you have the basic equipment (PC and personal fabricators, respectively). More will follow soon on my blog: http://www.erikdebruijn.nl/
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