Comment by t0mas88

My girlfriend works in a large grid operator (in Europe). According to her there are lots of regulations and contracts on the grid operators about how they must handle reliability. So it's unlikely that Facebook would be liable if this took down half the country, because then it was the grid operator not living up to their agreements on reliability.

There are a lot of automated fail-safes on this, and apparently larger industry (which a datacenter is as well) will get disconnected from the grid automatically in emergency situations before they drop residential areas. But in the end they will drop one by one everything they need to keep the larger grid running. It's not even a networked "smart" management system, the distribution points automatically react to voltage and frequency drops and they're set up to break some things like industry earlier than others.