I've been building on Facebook's platform lately, and some of the guidelines they have (rarely followed) started me thinking in terms of gradual information request, or a JIT users table.
Need the name? Ask for it, and store it in a cookie.
Need a persistent way to refer to a particular user? Use OpenID (or the Facebook UID, in my case). What if they don't have OpenID? Have links to a few providers, and also be a super simple provider yourself, built into your app. Don't store anything you don't have to.
As you find you need more information, ask for it, and explain why you need it. Make it easy for users to remove selective pieces of information if you don't need it anymore. Help them know when that is.
Need the name? Ask for it, and store it in a cookie.
Need a persistent way to refer to a particular user? Use OpenID (or the Facebook UID, in my case). What if they don't have OpenID? Have links to a few providers, and also be a super simple provider yourself, built into your app. Don't store anything you don't have to.
As you find you need more information, ask for it, and explain why you need it. Make it easy for users to remove selective pieces of information if you don't need it anymore. Help them know when that is.