This might sound like a good idea -- and I thought about it after I started playing with the N900 myself -- but even with four desktops, one can begin to get confused.

There really shouldn't need to be a way to add more desktops, as applications are their own desktops in a sense. So, you can open up several apps and switch back and forth between all of them via the multitask button. Then you can go to the desktop and flip between 1-4 of them...

Once you start adding more, you are really impeding the speed of operations by having to find, then select what you want.

Imho, of course.

Tim