Ronja, the optical data link device, is often cited as a failed open source hardware project — the last one mentioning it I just read is Lawrence Kincheloe’s excellent essay Musings Upon the Nature of Open Source Hardware as a Business at the end of his project visit summary at Factor e Farm.
Roja did fail (in the sense that it isn’t very widespread today not in the sense of being a cool open source project). One of the research studies I know of is the presentation “Ronja — Darknet of Lights” by Johan Söderberg at the 4th Oekonux conference for which Audio is available. The study is very interesting although I don’t agree with the conclusions. So why did Ronja “fail”?
Ronja’s main application was cheap internet access. At the time of its design in 2001 wireless LAN (Wifi) wasn’t yet available cheaply. And in the Czech Republic DSL wasn’t available at the time.
Now consider the technical characteristics of Ronja:

• Up to 10MBit/s
• Up to 1.4 km range
• Light: Doesn’t work in fog, or other bad weather (snow)
• Light: Hard to get the beam to the destination (direction)
• Light: Interference with daylight
• For full-duplex communication we need two (receiver + transmitter) devices
• sold for around 700$ at the time (the LED alone cost 120$ you get these for .75$ now)
• needed “a hell of a lot of time to build one” according to Söderberg

And compare these with WLAN:

• Up to 54MBit/s
• With good antennas several km range (I’ve built a link with 5.5km)
• Antennas are cheap and can even be built at home, e.g., a Cantenna — you can build a cantenna in an evening
• Works in fog and bad weather
• we need only one antenna at sender and one at receiver
• WLAN is very cheap nowadays, it became available (with new frequencies) in 2005 in cz.

So I think that Ronja “failed” because it was replaced by something better and cheaper that was readily available. It isn’t an example of a failed open source business model for hardware and shouldn’t be used as an example. This doesn’t mean that we already know how a business model for open source hardware should look like, though.
The idea behind Ronja — according to the Wikipedia article on Ronja “User Controlled Technology” is (mostly) achieved with WLAN technology today: We can use cheap devices and modify them (using open source firmware and homegrown antennas) to suit our needs. And there are large wireless communities now like Funkfeuer in Vienna who do their own Internet communication.