As any active software developer, I tend to have a lot of projects laying about. With the advent of Github all of these projects now live in the public eye.
For me, as the author, it isn't dificult to keep track of which project is in which state of production. For the casual visitor of my project pages this is a different matter.
To help passers-by to identify how solid a certain project is at-a-glance, I felt it would be prudent to offer them a "Badge". Some uniform way of knowing what to expect of the code in the repository without even having to look at it.