I totally agree with you (the first part). It's all calculated risk, and evaluation of cost.. you keep it up when the math works out. If it's down and it hurts your customers to the point that they'll walk.. it's on you. Bad math, your problem.
I speak as someone who's worked primarily in healthcare building services where I assure you we held ourselves personally responsible for natural disasters.
So it depends on your app. If my startup lets people take photos of their dessert and paste lolcats on them, then maybe my hosting goes down and I show my users a page that says the server must have farted, who cares.. but the last thing I'd do is show a page that said the people I pay with their money must be fucking up at the moment and we'll all wait together for things to get better.
Point is: My users are not my peers, they're my responsibility and livelihood. Even when something totally out of my control occurs. Fuck, especially when something out of my control occurs.
It is their fault. The company could have used global load balancing with the app hosted in multiple geographically distributed data centers in multiple national jurisdictions through multiple independent providers. This would ensure that the earthquake which leveled Amazon's California data center and the flood which took out Hetzner's data center in Germany and the martial law declaration which took out Linode's Japanese data center and the bankruptcy which closed down Rackspace's Amsterdam data center has no operational impact on Peer1's data center in New York where the service continues uninterrupted. As the data is fully synchronized between all data centers, the company keeps running, all customers are online, and the company can work on setting up additional redundancy in a Canadian data center to make up for the others which were lost.
Yes, this costs money. It's why people accustomed to getting everything for free on the internet can't fathom why larger companies charge six or seven figures for a service that they could roll out themselves by installing an open source package on some Linode VM. If you're paying that kind of money for the reliability, it's because you're extending a promise to your end customers, and the service contract you receive from your provider should come with lots of guarantees and financial penalties if the conditions warranting the price tag aren't met.
It is absolutely your fault if the site does down due to natural disaster. This is why companies who are large enough to do so host the site at multiple locations with the ability to failover.
Customers usually don't care about the reason for outage. They gave you money. If the service is running, good. If it's not, you screwed up. No matter what actually happened, you should've been prepared. Sad but true.
"No matter what actually happened, you should've been prepared."
This is just plain false. Being prepared comes at a cost. If you over-prepare, then your customers have to pay more for no good reason, and they don't necessarily want to. You have to draw a line and make a judgement call.
There are such things as natural (or political) disasters so serious that it would be extremely stupid to plan for them. And there are other disasters in between this and run of the mill. Again, it's a judgement call. And it's not your "fault" if the customer wants a combination of low price and reliability, and you made a reasonable tradeoff in order to achieve it.
As long as you are being honest with your customer and explain this somewhere.
The problem is one of expectations, if you don't say anywhere what have you prepared for and what are you going to do when something you didn't prepare for happens, you are misleading the customer, as they will rightly assume you have prepared for most ordinary things (heroku outage, for instance.)
It is false. Most of the time, at least. But then again I wasn't expressing my opinion but a probable opinion of Your Regular Customer.
Yes, Heroku should put up a different error notification when the problem is on their side, but I doubt it would make that much of a difference in the eyes of the user.
The information is useful. Heroku should provide it. We're done here.