Connected personal computers mostly disrupted pure-information businesses like music and travel agencies. But 3D printers will strain even endeavors that require a physical component. From Peter Frase at Jacobin:

“Like the computer, the 3-D printer is a tool that can rapidly dis-intermediate a production process. Computers allowed people to turn a downloaded digital file into music or movies playing in their home, without the intermediary steps of manufacturing CDs or DVDs and distributing them to record stores. Likewise, a 3-D printer could allow you to turn a digital blueprint (such as a CAD file) into an object, without the intermediate step of manufacturing the object in a factory and shipping it to a store or warehouse. While 3-D printers aren’t going to suddenly make all of large-scale industrial capitalism obsolete, they will surely have some very disruptive effects.

The people who were affected by the previous stage of the file-sharing explosion were cultural producers (like musicians) who create new works, and the middlemen (like record companies) who made money selling physical copies of those works. These two groups have interests that are aligned at first, but are ultimately quite different. Creators find their traditional sources of income undermined, and thus face the choice of allying with the middlemen to shore up the existing regime, or else attempting to forge alternative ways of paying the people who create culture and information. But while the creators remain necessary, a lot of the middlemen are being made functionally obsolete. Their only hope is to maintain artificial monopolies through the draconian enforcement of intellectual property, and to win public support by presenting themselves as the defenders of deserving artists and creators.” (Thanks Browser.)