has written a great post
on some of the issues surrounding open hardware and the differences between hardware and software. As one of the comments below notes, the possibility of well-documenting prior art is absent from the analysis, and is another avenue for preventing patenting of design ideas.
I think that this area of thought is wide open for some scholarly legal discussion, and I'd like to see a law review or journal article on this topic. The jury (so to speak) is clearly still out on this one.