These are good points. Yet I also suggest that monarchies, any kind of feudalism and for that matter republics, religions and democracies are maintained by Slytherins. In the case of monarchies and feudalism in particular all changes in power are more or less the outcome of Slytherin machinations.
Feudalism feels more like Gryffindor to me. It was more about personal authority than about cunning. Not to mention he was the one with the sword.
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: