Windows CardSpace is a feature included with Microsoft Vista. You can find Windows Cardspace under control panel. The Advantage of Cardspace is that it gives you a place where you can store all your personal or business information on the computer and exchange this information quickly with sites you log on to frequently. Basically, it will send the data to the site you log in without you having to type the information again or it will send the data to the new site you want to register with without you having to type the data again since its already stored with Cardspace.
Not sure how many people will feel safe about this feature, but as I said before, there is so much about us is already available on the Internet, sooner or later this type of services will be so common that everyone will be using them.