First of all why does the cloud need to be a central server somewhere outside of your control? You could have a password repository that you share between your devices and you just poll your desktop to update your passwords to your smartphone or something similar. Multiple accounts as mentioned earlier is easily handled by the browser maintaining a list of identities and prompting you for which one. To the security issue, why do your passwords need to be stored in clear text on the cloud, whatever form it takes? Could we not have them stored encrypted with your browser password also being the key that decodes your stored cloud passwords?