If the Internet is the computer, if the cloud touches down on the desktop, the security will be the first thing to protect. How is my credential stored? Is it safe?
In the current Beta 1, the credentials are stored in the user's local profile (Documents & Settings) with Windows Data Protection. If someone can logon to your machine and get access to your documents. This is vulnerable. But if someone can physically control your machine, what is not vulnerable?
To make it not vulnerable even when the PC is compromised, we need 2 factor protection with an optional password. By using Windows Data Protection with the additional password, it could offer more comfort. However, your IE remembered password may not be password protected. If you Firefox is not using a master password, the remembered password is vulnerable too. If you write down your password in Notepad ... All 1 factor protections depending on a windows logon prompt are vulnerable if the threat model includes the PC being compromised.
Security is a big thing. Let's do another review before releasing Beta 2.