You wouldn't hire someone based on their resume alone but a resume is usually required. What you're saying is Github is now a requirement which is absurd.

Also this would mean I have to use a particular tool for development (maybe I should be required to only use gcc for my C projects too). A particular tool on a particular site. I like Mercurial. The projects I like to contribute might use Google code. Guess I am going to have a hard time finding a job now.