"Dangerous" is refering to the danger to his reputation, the danger that he will be shown to be wrong and in 20 years perhaps look back and say, "Gee, I didn't see that coming." Just like the movie producer in the 20s who said no one would ever want to hear actors speak.
Find me a quote. I know of no producers who said such a thing. I think a far better example would be this: http://en.wikipedia.org/wiki/Smell-O-Vision We remember successes and look back and go "of course they were going to be successful." We seldom look back on failures and go "yep, everybody called that one."
Yeah, I'll cede there's plenty of bad ideas. I don't think 3d printing is one of them, I think we'll printing all kinds of things, including houses and cheeseburgers. No, not with the current nylons and acrylics, but the tech is on the march, and it doesn't take a huge leap of imagination to see the day when 3d printers are aligning molecules precisely to create whatever the hell we want. Suppose you wanted to make a superior sword. Can you imagine a day when a 3d printer can arrange each particle of material to achieve optimal atomic arrangement of iron and carbon to create something far superior to something that can be created by the world's greatest craftsman? It's a not even a big jump from that to printing the perfect cheeseburger. The author can't see that. I think that's his limitation.
Warner Bros. was already investing in sound. Harry Warner believed that the sound that would sell movies was music, not prose. His mistake was artistic, not technological." http://www.usatoday.com/tech/columnist/kevinmaney/2005-07-05... Jack Warner was talking about "The Jazz Singer" which his company was releasing. Again - a little knowledge is a dangerous thing. "uppose you wanted to make a superior sword. Can you imagine a day when a 3d printer can arrange each particle of material to achieve optimal atomic arrangement of iron and carbon to create something far superior to something that can be created by the world's greatest craftsman?" No. Because, you see, I had to take two five credit courses in steel to get my degree and I know it doesn't work that way. You make steel strong by working it. And, if I can make steel strong by working it, I can make things a hell of a lot cheaper than "printing" a sword molecule by molecule. 'cuz that's the thing - cold forged steel, hot forged steel, machined steel and cast steel are all very, very different things, above and beyond what's in the steel. And I can control that stuff with '20s era technology. The article is talking about 3d printing. You're talking about Star Trek-style replicators. There's a difference.
The day will come when printers can place atoms exactly and you can print an atomically perfect sword. Cheaper, faster, and easier than 20s era technology.