I think the same logic applies to 3-D printers. How? In the one case, you have a situation where it is no longer necessary to have (or produce) the "thing" in

I think the same logic applies to 3-D printers. How? In the one case, you have a situation where it is no longer necessary to have (or produce) the "thing" in order to use it. That is to say that you no longer need the CD/DVD or other physical medium in order to use the bits they carried. Printed (or otherwise rapidly prototyped) physical artifacts are quite a different thing. Having the 3D model or CNC cutting paths of a physical thing is in no way equal, or even equivalent, to having the thing itself. If the time and cost involved in making a replica is greater than the time and cost of popping down to the shop to pick up the genuine article or of ordering it online and waiting for delivery, then printing's not at all cost-effective. That's not to say that 3D printing (or subtractive RP) has no utility at all. One of its advantages is that it can be used as a relatively cheap substitute for maintaining parts inventories over extended periods of time—but only for some types of parts. And it is a good way of distributing low-volume decorative works, since the print price is not much higher than the per-unit price of low-volume tooling. (Or at least it will be when the resolution is sufficiently high, since most users are not likely to want to spend a lot of time chasing and filleting their print results.)