I think it would be a great feature to enable access to the dropbox folder through a password protection option.
That way the files could be protected from view if another person has access to my account.
Say another person uses my computer when I am away on vacation. It would make sense in this case to temporarily lock it from view.
I am aware that you can remove folder from syncing.
Although it can still be toggled on and off by anyone who has access to my computer.
Not protected enough.