Not at all.
> Companies that depend on Facebook advertising would disappear.
Good.
> People would be locked out of OAuth accounts on thousands of websites.
OK? If you were federating your auth via Facebook it was only a matter of time until you were locked out for one arbitrary reason or another. This just seems like an acceleration of a good thing.
> It would be catastrophic.
From your perspective, I can see that. But there are other perspectives out that that are not completely beholden to Facebook.