Over thirteen companies in this world deal in open source hardware and are all million-dollar companies. Though, the ideology of open source hardware has not become popular yet due to ignorance. However, things have started changing and open source hardware will see more acceptance very soon.
Unlike open-source software, because there have been no formal definitions, many people may not even be aware of the growing industry. But already some of those practicing its general principles have become household names among the geek set: Arduino, the programmable single-board microcontroller and software suite; Chumby, a popular Wi-Fi device; MakerBot, a low-priced 3D printer; and Adafruit, a maker of do-it-yourself hardware kits for things like MP3 players and more.
The first step to this is issuing a formal definition of open source hardware and the change is already in place. open source hardware has been formally defined as given in this page.
The formal definition will go a long way in establishing businesses around this ideology and popularize it. This video on Open Source hardware gives an overview of the concept.
We hope to see more such popular businesses based around open source hardware.