Is this an idea whose time came decades ago? Well, now there is serious work being done to make it real.
Web sites, including this one, insist on your profile information. As web sites become more specialized, customers/visitors will be filling a registration a day!
That, unfortunately, is the beginning of the problem. Keep the same userid and password across websites - suffer the consequences of being hacked once and robbed many times! Keep different userids and/or passwords for all the sites you access - well, you might need a website to hold all these userids and passwords! So what is the way out? The answer, as always, is a simple matter of looking at the root cause of this problem. You are one. Your profile is the same. Keep it in the same place - let everyone access that one place. Microsoft Passport was a good idea in this direction. OpenID is another one with more traction. Read On>>