If you have a business use for what they can print today, you already have one, and are likely contemplating buying a better one. If you have a personal use for the parts they can print, you probably already own one. And even if you don't have a real use for them, you may have one as a cool toy. But not everyone is going to buy the same toys as you.

Once they get a lot more capable (maybe not Star Trek replicator capable, but substantially better than they are now) then they'll become ubiquitous. Until then, not everyone needs one. I'm thanking you now for being an early adopter, but don't expect me to join you yet.

The problem is they're too limited. They have to get more capable, not faster, in order to meet my needs. If they can insert circuitry, maybe I can print things that are somewhat more useful. As of right now, I have needed exactly one 3D printed thing (a battery holder for an electronic project, which a friend provided gratis.) But at no point in the last five years have my needs for small plastic things added up to the $300 price of a Simplebot, let alone a printer with better quality, resolution, size, or capabilities.

Maybe you have kids who need thousands of plastic army men. Maybe you are in a business where fabricating prototypes is valuable to you. Great for you, I'm glad you have a use for one. Hopefully you'll help drive volume so the costs come down even further. But as they stand today, they're too expensive for anything I need, and would take up more storage space than I want to waste on a toy.

It has nothing to do with thinking big or small. I'm sorry you can't imagine a scenario different from your own experience.

None at all. Drivers aren't that stupid, and still maintain enough control over their car to react appropriately.

You, however, might be so stupid that you'd slam on your own brakes to 10 MPH just to make another idiotic point, at which point you get rear-ended by an 18-wheeler who is unlucky enough to be following you. Fortunately, there is only one you, so the gene pool will be thinned out to the point where this situation won't repeat.

I simply don't need a bunch of small plastic tchotschkies, no matter how fast I can print them.

There's a big difference between uranium and a working hydrogen bomb. The US won't use nukes unless someone else detonates one first.

Ford has had that for years now. It's called 'Adaptive Cruise Control', and uses radar to maintain a preset minimum following distance.

I have it on my 2011 Ford, and while it's nice, it can only be set to following distance, not time. I want to set it for a two second gap, but my choices are 22, 44, or 66 yards. It's too close for high speeds, but too long for low speeds.

(sorry, Dr. Ford, not Broad)

Devil's Advocate here, but maybe the reason is that all kinds of data is out in public, and some of it is likely flawed. Maybe there's a paper that theorized that you could set a Dewar's flask of liquid hydrogen next to an A-bomb to get an H-bomb. But Dr. Broad is a respected authority, and if he says "we did it this way" without mentioning the Dewar's flask idea, a rogue state would know what not to try.

Remember, these guys get about one shot to get their test explosion right, because in about an hour after a successful test of an H-bomb by anyone the US considers a threat the USAF is going to be raining actual working H-bombs on their entire nuclear program, with a few diverted to cover the presidential palace, the parliament, and essentially every researcher and civilian within a 20-km radius of the aforementioned targets. The US will not tolerate a new state of MAD with a new non-Western-approved government.

Remember that the bag's Zigbee radio is broadcasting the bag's location constantly in real time, whereas the child's embedded GPS transceiver is using an accelerometer to help predict when the child will zip across the roadway; plus the child's Wi-Fi chip, network path, etc., will all add latency. If that child's GPS receiver has lost signal due to interference, it's going to need to rely on inertial navigation and its own free-running clock to send the predictions of future locations to the car, and those might be out of sync, depending on how long the child has spent in the basement.

Oh, wait. Children aren't having embedded ADS-B chips surgically implanted yet? And random trash bags don't have Zigbee? Hasn't someone been thinking of the children?

I heard a great quote from a filmmaker who encouraged his cameramen to take big risks: "If you're going to soar with the eagles, you can't expect to crap like a canary."

They shot mountains of unusable trivial footage, which cost them a ton of cash. But they also produced some spectacular, memorable films, which catapulted them and their clients to huge popular success. He realized that he had to risk his business to succeed, and he won. Not everyone who takes those kinds of risks succeeds, but companies that take no risks generally don't explode with success, either.

One alternative is to abolish fines, and send people to jail for an amount of time relative to the infraction. Everyone gets about 22,000 days [source: The Moody Blues] so the punishment would be equal regardless of income, right?

As others have said, every person is different in their abilities and limits. And I know nothing about your friend's situation, so I can only tell you about the situation I've worked with.

My aunt was born with cerebral palsy, and she has always had much better control over her feet than her hands. Her solution was to place an ordinary trackball under her desk, (the large kind, not the marble sized one) and she uses her bare foot to control it.

Because it's foot operated and she can't really clean it effectively, it gets dirty much faster than a desktop trackball, and so she ends up replacing it more often than you would a mouse. But overall it's been a pretty cheap investment, and one that works for her.

It'd be pretty easy to do, really. Create a quarantine VLAN, and if someone's spewing bad packets, flip them into it. Once inside, there could be all kinds of safety rails. All DNS requests would be hijacked and rerouted to the ISP's special quarantine DNS server. Packets would only be allowed to destinations where a valid DNS request was previously made. No routing would be allowed through the network: all packets must either have a source or destination address within the VLAN. SMTP traffic would be restricted to a few per day, with only a few recipients per day. Some destination ports could be closed, such as IRC. If they were DDoSing a site, perhaps with the LOIC, the address for that site would be completely unreachable from within the VLAN. The account holder would get warning SMS and Email messages, and all port 80 web traffic would be silently proxied and injected with scripted pop-up banners. They would say something like "Some computer on your home network is attempting to damage other computers on the internet. This is likely due to a computer virus or other computer infection. In order to restore service, and avoid falling trap to an online scam, please telephone us immediately using the phone number printed on your most recent billing statement from BigISPco. Your internet connection will remain severely limited until after you have your computers repaired and cleaned, you call us to restore service, and we verify that your computer is no longer attempting to attack other computers."

Long time ago I had a co-worker who made a mistake where he lost a lot of un-recoverable data. He went in to our boss to offer his resignation. My boss said "Hell no! I just paid $100,000 for you to learn that lesson, so now I need you to make sure that kind of thing can't happen again."

That's not enough. A drone could be flown autonomously using inertial navigation, or even dead reckoning, needing no external RF guidance. They have to be able to bring them down without praying that jamming all RF will work.

On the other hand, hobbyists have had model rockets for 50 years and there's been no rain of home-made ballistic missiles on the White House. Maybe it's just not a big deal.