You may want to avoid using Dropbox's mobile app If you sync sensitive data with your Dropbox account — particularly when you're connected to a public Wi-Fi network. Instead of using the considerably more secure HTTPS to transmit file metadata (like the desktop app), Dropbox Mobile sends data unencrypted over an HTTP connection.
According to Dropbox, this is due to performance considerations and may change in the future. For now, it's something you may want to keep in mind. [Grepular]