[marcan_42]

Ex-Googler here.

Yes, apps are highly distributed. Yes, roll-outs are staggered and controlled.

But some things are necessarily global. Things like your Google account are global (what went down the other day). Of course you can (and Google does) design such a system such that it's distributed and tolerant of any given piece failing. But it's still one system. And so, if something goes wrong in a new and exciting way... It might just happen to hit the service globally.

When things go down, it's because something weird happened. You don't hear about all the times the regular process prevented downtime... because things don't go down.