title: Use case of openID
body: <p>I am a bit confused about the use case of openID.</p>
  <p>say, if a user login to a web application using openID. Should this web application create an account for the user?</p>
  <p>1). if it should, then what is the difference between using openID and using OAuth (set scope to &quot;profile&quot;) to get the information of the user and then create an account for the user. (later login can use unique key from profile/id token to find the user in database)</p>
  <p>2). if it shouldn't, then if the user logout, and then login using openID again, all the activity the user previously did (for instance, saved some article for later reading) has gone (assume no cookie/session is set, since they are limited to one device). if so, what is the point of authentication under this scenario</p>
  <p>I understand openID is an extension of OAuth, specifically designed for authentication, but when and how should I use openID for authentication?</p>
  <p>thanks</p>