Nice idea, but there's a catch... Simply uninstalling and reinstalling F&F would remove any protection. The PlayBook has no secure, persistent storage that apps can use and that remains intact through uninstall/reinstall.
I downloaded this because I have important work documents in my dropbox.
Is there a way I can secure the "files and folders" app itself?
Simply do not allow F&F to save the dropbox login info.
Also, why not password protect your PB. That's what I do. What I have on my PB is no ones business but my own.