I'm working on a fun project with friends that we would love to see fly (We're applying for YC by Tuesday probably !). As a developers, I relate best to the technical kind of dept. It's interesting to read about other kinds of depts that you will have to pay back when you deal with a startup, pre-launch, and post-launch. Funnily, they all seem as important to keep track on.
Financial dept => game over. Personal dept => burn out => game over. Mental dept => burn out => game over. Technical dept => quality/productivity freefall => game over.
Let's map them the to the assets of a startup. Out of these four kinds of depts, 2 depend on the people and not the skills. Financial depends probably equally on skills and people. Technical dept being mostly skills related.
I think it illustrates well why having a great team synergy is so crucial to success.
What other depts can you think of?