This is something I learned both at my first tech job and in reading about the quest to make the "lightest possible Windows installation" for Hotmail: if you don't pay any attention to your dependencies, you'll eventually code your way into a huge ball of spaghetti. At some point systems get big enough to start falling out of your head. By the time I noticed it happening to me at that first job--when I had trouble keeping the relevant subset of the system in mind--my productivity dropped by an order of magnitude. Having a visualization like this would have been handy to help see it coming.