“The announcement that they are able to decrypt the files on behalf of the government contradicts their prior public statements. They claim that Dropbox employees aren’t able to access user files.
This announcement means that Dropbox never had any mechanism to prevent employees from accessing your files, and it means that Dropbox never had the crypto smarts to ensure the privacy of your files and never had the smarts to only decrypt the files for you. It turns out, they keep their keys on their servers, and anyone with clearance at Dropbox or anyone that manages to hack into their servers would be able to get access to your files.”
via Dropbox Lack of Security – Miguel de Icaza.