Several openid providers do use them to identify users. For example see link on https://www.myopenid.com/signin_password https://www.myopenid.com/signin_passwor

Several openid providers do use them to identify users. For example see link on https://www.myopenid.com/signin_password https://www.myopenid.com/signin_password Also, I've heard mention that Monkeysphere is working on something to generate client SSL certs that are tied to your gpg key. Which would allow logging into a site with one, based on the web of trust.