This just shows how fragile the whole oEmbed idea is (as any reliance on third party services in your content really) One day it is there, the other it is gone and you get zero notification that it happened while your content remains broken.

To be fair it probably happens more with youtube videos being blocked for some reason, but the baseline assumption that twitter /FB/youtube will be around forever is funny. The whole idea of using wordpress is to control your own content. Using oEmbed says that you just don't really care about that.