Usability and cost are the biggest concerns. It might even end up being less secure. You have to carry your key pair with you and import it into the browser any

Usability and cost are the biggest concerns. It might even end up being less secure. You have to carry your key pair with you and import it into the browser anywhere you want to use it. You have to make sure you delete the key (securely, ideally) before leaving the machine. What is the guarantee that the machine you are trying to use is not compromised or holding on to your keys? Even then the website is not sure if its really you. They also need to implement a password based authentication. Some one stealing your keys is more possible (given that you want to login from any machine) than some stealing your password. Of course they can guess your password but I won't get into that. One way to do it would be to build a dongle that has keys and provides the authetication service on behalf of the user. But then we would need multiple identities, which means we need multiple certificates and the cost will multiply. Anonymity is completely gone. Even if the CA grants you an "anonymous" certificate it can always be traced back to you based on the cert parameters. So no.