I'll take a stab at this. Register: Username, Password, Hacker News Profile URL. Click "forgot password" link. Message: Modify your HN profile to include the

I'll take a stab at this. Register: Username, Password, Hacker News Profile URL. Click "forgot password" link. Message: Modify your HN profile to include the phrase "RandomTextPleaseLetMeIn". Click on "Verify me from HN". The system lets you in. Now change your password. Edit: Instead of HN profile URL, you could also use Delicious ala 'save the following link with this tag "RandomFunk" to your Delicious profile'. The goal is to prove to a website that has read-access something to which you have write-access. This something is shared between you and the website before hand (at registration).