I just had a great idea! Sites like Amazon ask for your email address and password. Now if they asked for your Jabber ID they could request your VCard (or any future profile system we get going) and automatically populate your shipping address, name, and everything else that they want and you're willing to give. Combine that with the XMPP/HTTP authentication JEP they don't even need to ask for a password.

Granted privacy would be a concern, so I can imagine putting in my JID at the site, and then my client would popup a dialog telling me that Amazon is requesting my address, name, and phone number. I don't want them to know my phone number, so I uncheck that and let them retreive all the other data.

Since my address could change, and I don't want to enter it into their site this might as well use pub/sub. Then they'll always have my latest address for greater or worse. All I had to do was enter my JID and click OK to get introduced and signed in.