Earlier quoted context omitted.
Why would you ever expose the sync folder publicly? Just keep a copy on a local computer with Dropbox if need be.
Because I only have one computer and no mobile devices— therefore I only have one copy of the password database, and I need the password database to access Dropbox. The sync folder is encrypted—is there some risk I'm not seeing?
For you, I would just keep a copy elsewhere (friends computer etc.) or just get an additional device (mobile or otherwise).