This is a lesson about the difference between hosting your own apps and hosting customers. All internal Google apps are designed to survive failure of an entire datacenter, so it sounds like they reuse that mechanism for maintenance rather than the riskier practice of maintaining a datacenter while it's live.

Getting back to Verizon, I work in an "enterprise" and scheduled multi-day datacenter maintenance tends to happen about once a year. Many of Verizon's customers would probably have no problem taking down their infrastructure for a weekend, but they feel helpless when someone else does it to them.