I got this error while trying to do a manual backup of a company mailbox :)

One day I'll have the time to write that script manually

https://www.backupify.com/ do this for Google Apps - works pretty well.

Your contacts' email addresses (or at least most of mine) wouldn't do you much good if everybody left gmail all of a sudden.

You should definitely do backups.

But I'm pretty sure that in the vast majority of outages you'll suffer with gmail you won't have the time to recover you're backup before the service is back up.

That said, you should definitely do backups. It's just that it wouldn't have helped in this case.

Also, backing up Emails is super simple, just fire up any mail client ...