Drupal Association members fund grants that make connections all over the world.
When the callback from the authorize returns to the callback URL (e.g. the client app), currently it only returns the
oauth_token. As per http://tools.ietf.org/html/rfc5849#section-2.2 this callback also requires
oauth_verifier. (I recently ran into a case where a client was expecting to see this since the spec requires it and failed to callback, in which authentication could not happen).