Can't see this working for things like logging in to leave comments or play games like Twitter and Facebook identities. Where I can see it working (and working

Can't see this working for things like logging in to leave comments or play games like Twitter and Facebook identities. Where I can see it working (and working well) is SaaS subscription services - it streamlines the signup process, provides additional data to the provider and pushes signups towards Paypal (and away from merchant account or other providers).