The similarities between the early era of personal computing and the current state of 3D printing are huge.

When personal computing was in its salad days in the late 1970s, it was a fringe interest for weirdos with beards. While it had its share of true believers who envisioned a world with a computer in every home and school, there were just as many skeptics asking the question, "What is this and who is it for?"

Now 3D printing seems to be going through the same thing.

A 3D printer is a machine that builds physical objects bit by bit, layer by layer—similar to how inkjet printers lay down colors on a piece of paper, but in three dimensions. Commercial versions of such a device can cost tens (or even hundreds) of thousands of dollars, but devoted hobbyist groups have continuously tinkered and optimized the device, reducing the cost to less than $2,000 (and in one case, just a mere $400).

So we have a very expensive and exclusive device normally reserved for large businesses starting to pop up in people's homes. No one's quite sure what it's good for, but a few believers see the potential for a general-purpose creative device.

See the similarities?

The man leading the charge seems to be Bre Pettis of MakerBot. His company introduced the MakerBot Cupcake in March 2009. Now, three and a half years later, MakerBot is selling its fourth generation of printer. Pettis is on the cover of Wired.

Smaller companies such as Printrbot have sprung up in MakerBot's wake—in fact, the New York Maker Faire included a designated area called the 3D Printer Village for these companies to showcase their products.

The market for 3D printers in the home is still pretty niche. Tinkerers use them to create custom parts for other homebrewed creations. A site called Thingiverse, also maintained by Pettis's MakerBot, serves as a popular community for users to exchange 3D object files.

That exchange may be crucial for 3D printing to go mainstream.

In 1979, spreadsheet software VisiCalc legitimized personal computers as a serious business tool. The mainstreaming of 3D printers will occur when people realize they can print doorstops and shower curtain rings, when they realize that owning a 3D printer means no longer having to drive to the store to buy something manufactured in China, put on a boat, loaded into a truck, and dropped on a shelf.

A small group of tinkerers launched personal computing. But people who didn't want to write their own code are the ones who turned it into a mass market. As Steve Jobs put it, "the computer for the rest of us."

When 3D printer makers create a make-anything machine for the rest of us, it's just a matter of time before there's one in every home and school.

Don't miss: 11 Crazy Things You Can Make With A MakerBot >