TweakTown writes Microsoft will be incorporating a password manager into Windows 8. The feature will use the Live ID as a master password, and will enable syncing to all other Windows 8 machines you use.
The Live ID password is all you'll need, so for the multiple websites you use, you can set very complicated passwords for them, in the case you get hacked and your credentials are stolen, your entire digital life isn't ripped away from you. Windows 8 will automatically enter your login information when visiting a saved website.
There are similar services and apps available that do this, examples are 1Password and LastPass, but being built into the OS is a much better option. What if your Windows Live ID is stolen or lost somehow? That's fine. Microsoft are including a bunch of safety features into Windows 8 that are designed to detect compromise and limit account usage until you can recover it.