I'm not really sure why everyone is so enamored with this idea.
Its kinda techno-sexy, sure, but this isn't the groundswell of democratizing force that it is being made out to be. Its not even a foreshadow of it.
See, I think that's where you're missing the point. You're like IBM, commenting on the microchip, saying "But what is it good for?" The point isn't about making guns, or at least, that's how you and I see it. But this definitely is the beginning of something truly astounding. Today, it's plastic guns that break. Tomorrow, it's carbon nano-tube cutlery that lasts an eternity until you recycle it into a new sprocket for your bicycle. That you printed. The next day, you're printing your own cell phone, a cute little antique.
Sure, the printers in two days won't look like these. They won't operate in the same manner. It's like we're in the days of ENIAC. But ENIAC was commissioned in 1946, and today, 67 years later, there's enough computing power in your smart phone to launch the space shuttle.
So, yes, we can pooh-pooh the little plastic toy gun. It's ineffective and inefficient in every conceivable way. Well, every conceivable way save one: it opened a door that liberated popular imagination. (Cause, you know, it's not like this is the first thing ever made by a 3D printer. I mean, a dress from a 3D printer debuted in Paris just a couple of weeks ago. So, you know, there's that.)