It is inevitable that this will happen from time to time. What it does prove is that the more data we entrust to the cloud, the more important it is that we have reliable backups in place.
A similar crisis occurred when Amazon Web Services went down almost exactly a year ago; thousands of web-based businesses rely on Amazon for their storage services and after two hours of downtime, users were observing that cloud computing can't become mainstream, certainly for businesses, until it becomes almost infallible.
Within minutes of the Gmail downtime unfolding, I was sent a very pertinent message on Twitter speculating on the cost of the problem:
"Let's count the cost: 25m users, 33% affected; average of $50 per hour lost productivity = $415m per hour economic cost..."
Jemima Kiss via Twitter.