"Well what's more important? Security of data or your customers not being able to buy a pair of tights at 3am (which may be mid-afternoon their time)?"
There. Fixed that for you.
If you are using the cloud in a large-capacity way, you are probably providing some sort of service to many people. Movies, music, sales, blah blah. Now you could run this from your server room with a big fat pipe to handle the bandwidth; but one nasty lightning strike or flood or misplaced backhoe or trigger-happy ex-employee could take you offline. Perhaps for good.
I'm no fan of the cloud for personal computing, I prefer my photos to remain on my device; but when it comes to a large business, there may be something to be said for running the services off-site spread across computer units potentially at different sites with the ability to scale up and down according to demand. You can't expect it to be 100% available, you couldn't say the same for your own server room. That said, it is perhaps by way of embarrassing and public cock-ups like this that the system finds itself flailing in the midst of a real life stress test, and once the issues have been identified and solutions devised, may be that much more reliable in the future.
I should remind you that a huge swathes of mainland Europe were plunged into darkness in November 2006 after some Germans switched off a power line to allow a ship to pass (nothing unusual there) which somehow triggered a massive cascade failure - https://en.wikipedia.org/wiki/2006_European_blackout.
Even with well designed systems, things are going to be out of spec and things are going to go wrong. We hope the system is well enough designed to cope, but like a computer crash when the kernel stack is trashed, sometimes the only possible result is a failure. Let's hope for the next time, the situation was identified and is better handled so that it won't bring the whole thing to its knees...