I don't know... why should I worry about Dropbox security in this context? The risk that someone could steal my Dropbox data is of course there, but that they then would be able to decrypt the password database (or bother to spend resources on trying) seems very unlikely.

The only thing I'm a bit worried about is accidentally deleting or corrupting the password file, as Dropbox could then synchronize this change across all devices. I guess I should back it up regularly to non-Dropbox folders to avoid losing all my passwords.