git branch diagram

I am trying to get my employer to start using git and have found the distributed model and git's branching to be one of the hardest parts to explain and understand. I put together the attached diagram (done with graphviz so some things are not in the most logical place) to help explain things to my coworkers.

Unfortunately, I don't understand things well enough myself to know if the diagram is correct or not. I read in the stgit docs that developing directly in the master branch is discouraged by convention, but I don't really understand why. The git tutorial shows work happening directly in master, so I wasn't sure if that's a convention that only makes sense for stgit or for plain git, too.

In my diagram, I am assuming that most developers work in master, and make branches for their own long-lived projects and experimental things.

Does my diagram make sense? Are there any suggestions or corrections?

Thanks, Patrick