Elon Musk posted All Our Patent Are Belong To You  in the Tesla Motors blog.
His arguments are familiar with those of the software open source industry: You can’t rely on big companies to truly advance technology. In the software industry, many modeling tools are still based on mid-1990s approaches and technologies, which is similar to Big Auto’s continued preference for gasoline (or diesel) powered vehicles.
What that in mind, and to promote other companies in producing zero-emission cards, he removed all the patents from Tesla Motors’ patent wall and stated:
Tesla will not initiate patent lawsuits against anyone who, in good faith, wants to use our technology.
I also really liked another quote he made:
I realized that receiving a patent really just meant that you bought a lottery ticket to a lawsuit, I avoided them whenever possible.
We believe that applying the open source philosophy to our patents will strengthen rather than diminish Tesla’s position in this regard.
This must say something about the strength of the open source movement and its potential business possibilities!
Go read the blog post. It’s not too long and informative!
 See this wikipedia entry if you don’t get the reference.