I guess it depends on how you use the quad tree. if you had a large world which needed to maintain the position of all the objects within it then building the tree once and adding/removing objects would probably be more efficient. In my racing game both the vehicle and the view move, however, and most of the initial culling is done simply by ignoring everything which isn't visible (as there is no way the car will collide with anything outside the view). Because the view is moving it effectively moves the root node and therefore necessitates rebuilding each time. It's no real performance hit anyway, I can render over 3000fps on my machine at work
The quad tree node class is pretty flexible and I'm sure it wouldn't take much to modify it to allow for adding / removing objects as they move if anyone needed it. FWIW the quad tree code is based on
this article.
The car game itself has come a long way since (it doesn't even have cars any more...) and won't have a rotating view as I have very specific ideas for it. I'm glad you like what you see, however
Eventually I will post something about it in the projects forum.