"3D printing. There are lots of good 3D printers, and they're bought by the same people who buy milling machines. They're a useful industrial tool. But home printing? Not happening."

I don't know of many people using 3d printing as exclusively for self-use. Most are people making toys, games, or components for machines which they sell to other people. So, I don't see how 3d printing has been a failure of anything other than idiotic futurists that think it's the ST:TNG replicator (it's not). If anything, I think 3d printing has taken off like gangbusters with small manufacturers and small businesses. They reap the benefits of having a small plastics manufacturing machine that doesn't need vacuum mold dies swapped out or machined by specialized tools. Just because VCs can't turn it into an firm with a successful IPO doesn't mean it's a failure is all I'm saying.