One of my last productive acts when I was at microsoft was to get a two-line change committed in windows to a tree outside my org. It took two full months just to propagate the change up the very fragile and fractured tree of repos from my team's to WINMAIN and from WINMAIN back down to the owning team's org, and my efforts were required every step of the way. It was truly soul-crushing.

Edit: this was in the windows vista days and I hope/expect they have overhauled that entire process in a major way, because things were at a near standstill.