someday (hopefully soon) we will have so many applications to choose from for our Maemo-based tablets/mobiles, and then it will be very crucial to be able to create folders on the Desktop and in the Main Menu
I just have to add this everywhere the idea comes up: Having folders is a must for an application launcher, no matter if its Maemo's default applications menu or a third party app.
But:
If you think of folders, please also think of the way they are implemented correctly, following the freedesktop.org standard: as catagories in the .desktop-file of an application. (The user is free to change these default locations, of course, but it's a good start.)
Whatever work is invested in this area should, I think, re-use things that already work and that people (developers, in this case) are familiar with.