The thing is, multiple availability zones are in multiple data centers. We now know that they have a common failure point, but how could anyone have known that

The thing is, multiple availability zones are in multiple data centers. We now know that they have a common failure point, but how could anyone have known that before it happened. For all we know multiple regions could have an undiscovered common failure point. Don't get me wrong. Heroku isn't entirely blameless--I had a production app that was down for about 12 hours.