I need this too - it is impractical to show folders from the top level to members who dont get access to those folders. Why should they even see those folders? This is clearly a handicap of Dropbox feature - because if I can assign groups to certain top level folders only I would expect them to see only those folders they have access to. It looks very strange and I am sure they will ask questions on why they see the folder but cant have access to those.
Please DROPBOX developers do something about this !
I would like to see this functionality for my company as well. We use drop box with a number of outside vendors and although they don't have access to some of the team folders, the name of the folder can reveal things about our business that we don't want everyone to see.