3D printers--desktop devices that can print out objects as easily as your home inkjet prints out documents--are getting less expensive and more common every day, and they promise to revolutionize manufacturing in the same way that desktop printing revolutionized publishing.

I've written elsewhere about how we're at the start of a 3D printing revolution. In the past year, people have used 3D printing to tackle everything from spare parts to entire cars to blood vessels. It seems as though a new use for 3D printing emerges every week.

Unfortunately, though the promise of 3D printing is great, we've also begun to see glimpses of its dark side as criminals--and average citizens who are up to no good--think up dangerous and creepy new uses for 3D printed material.

How About Your Car Key?

When people can replicate any object with ease, you soon realize that there are plenty of objects you don't want replicated. Obvious examples are the keys to your home, office, and car--yet savvy 3D printer owners have already how to do just that: Measure the key, build a 3D model, and print away to produce cheap copies.

If you're the rightful owner, the technology gives you a hassle-free way to generate backup keys, but the process can go terribly wrong. For instance, a member of a German lock-picking group, Sportsfreunde Der Sperrtechnik – Deutschland e.V., used his 3D printer to create a key to unlock handcuffs carried by the Dutch police. Startlingly, he was able to measure and reproduce the key accurately by using nothing more than a photograph of the key hanging from the belt of a police officer plus some basic math to gauge its size. Afterward, he not only printed out a copy of the key to test, but also put the model up online for anyone to print.

The key was just a proof of concept by an enthusiastic amateur and hasn't been used in the commission of any actual crimes, but real criminals have discovered 3D printers, too. In September 2011, a gang was prosecuted after stealing more than $400,000 dollars using ATM skimmers. The gang's skimmers--devices that fit over an ATM machine and steal the debit or credit card information of unsuspecting ATM users--were created on high-tech 3D printers to help make the skimmer overlays for the ATM machines look as realistic as possible.

[Read: "Keep Your Credit Cards Safe From Skimmers"]

These criminals weren't the first to try bilking the ATM-using public. A similar ring was indicted in South Texas in June 2011 after investing some of its ill-gotten gains in more-advanced 3D printers. And last year a legitimate 3D printing service called i.Materialise received an order for an ATM skimmer that it turned down. "Fortunately, our engineers were quick to react," i.Materialise said on its blog, "and after communication with the customer, the decision was made to decline the order. We do not support criminal activity and will do everything in our power to prevent possible crimes."

While most consumers probably can't afford the kind of high-quality 3D printer needed to print out physical objects with the level of detail that these ATM skimmers have, even the consumer-oriented Thing-O-Matic printer from Makerbot, which retails for $1299, can print some pretty scary stuff.

For instance, a user on Makerbot's Thingiverse, a site where users share potentially useful 3D models for others to print out at home, posted the plans for printing a magazine for an AR-15 rifle. A fully automatic AR-15 can fire 800 bullets a minute. While the posted model held just five rounds of ammunition and was completely legal, extending the magazine to hold fifteen or even more rounds by modifying the model would be easy enough. Under the now-lapsed Federal Assault Weapons Ban, possessing any magazine containing more than ten rounds was illegal. In response, another Thingiverse user posted a model for printing a part called the lower receiver for the AR-15.

If, like me, you're not very knowledgeable about guns, that may not sound like much; but from a legal perspective, the lower receiver is actually a pretty interesting gun part. If you wanted to buy the parts for an AR-15, you could purchase at gun shows or from mail-order catalogs--without any sort of record--every part of the rifle except the lower receiver. By printing out the lower receiver of an AR-15 on a 3D printer, it's possible to complete construction a fully functional, unregistered AR-15.

3D printers can now help a bad guy break into your home, steal your money, and even assemble an unlicensed automatic weapon. Clearly it's time to pass some laws that limit what these things can do, right? Not so fast.

Another Point of View on 3D Printing

Michael Weinberg is the senior staff attorney and technology evangelist with the public-interest group Public Knowledge. He is also the author of It Will Be Awesome If They Don't Screw It Up, a legal white paper on the future of 3D printing and intellectual property. He says that, while some uses of 3D printers are obviously dangerous and illegal, we have to think about how much 3D printing is to blame.

According to Weinberg, "One of the challenges the 3D printing community is going to have is going to be to remind people that just because it involves 3D printing, that doesn't mean that it's going to be new. The ability for people to manufacture these machine gun pieces for instance has existed for as long as those pieces have existed, thanks to metal-working and milling machines."

All of the potentially misused items that people can create on 3D printers--the keys, the gun parts, and even the ATM skimmers--have been illegally manufactured in the past by means of traditional milling machines and other manufacturing hardware. In fact it's still probably cheaper and easier for the average person to gain access to metal-working tools than to a 3D printer. The number is growing daily, but at last count Makerbot, which probably is the best known manufacturer of consumer 3D printers, had sold only 5200 of them. A day may come when everyone has a 3D printer at home, but it's too soon to start preparing for that eventuality.

"Anybody who thinks they know what the world looks like with this is probably deluding themselves," says Weinberg, "There's a real danger from a policy standpoint that you'll start worrying about this before you even know what it is."

So for now at least, we may not want to regulate 3D printing--not because the potential for 3D printers to change the world isn't great enough to justify some sort of regulatory legislation, but because these uses are just the tip of the iceberg of what 3D printing can do. "It's not time to ignore 3D printing," says Weinberg, "but it's probably too early to start constructing the policy framework. It'd be like trying to regulate the Internet in 1992."

Just as it would have been impossible to predict the modern Internet from the barely connected world of the early 1990s, it's too soon for us to predict with any accuracy the real uses--and abuses--of a world where every home has a 3D printer. If we move prematurely to regulate 3D printers, we could fail to protect against the real dangers of the technology and at the same time limit the potential of 3D printing to change the world for the better.