It used some another (failed?) provider before (which connected accounts to Gmail, Yahoo, etc.)
If I recall correctly, Clickpass was a centralized OpenID proxy, whereas Persona is trying to bootstrap a fully decentralized protocol. We don't want to even be able to track you. :)
[Edit: Corrected YC cohort. Thanks wamatt!]
Then a few years later (2012), Yola sold the IP and users to Janrain [2]
[1] https://news.ycombinator.com/item?id=402973
[2] http://janrain.com/clickpass-acquired-by-janrain/
EDIT: my pleasure callahad :)
Where? I can't see it.
There are many ways they could have notified OpenID users that would have worked -- this wasn't really one of them!