Comment 20 for bug 881019

A slight comment on this

  Now, Launchpad is still restricted to a single provider. This means that
  multiple identifiers don't occur except when people mistakenly create
  multiple SSO accounts, log into Launchpad with both, and merge the two
  resulting Launchpad profiles. And it's not clear which identifier should
  win when merging profiles, so we keep both linked, letting both SSO
  accounts log into the one profile.

Actually, SSO does merge one account *into* another, effectively discarding the "source" account (the user will still be able to log in with the old email address, but only because that address is added to the "target" account). Therefore, the only valid openid should be target accounts one (ie, it is possible to know which openid the user will have after the merge).