Like anything else, webmail needs to have layered backups in place. I use Gmail (sparingly now that SMS is much easier for 75% of small comms) and download/backup all my email to a desktop client once a month. The desktop email client backup is then uploaded to my Dropbox account.

My SO employer's network admin today mentioned the Gmail incident and noted that every week, email servers go down and most do not have any proper backups in place and the end result is 1000's of accounts are wiped out. The reason we don't hear about these is due to the fact these email providers are not as big as Google et al and thusly do not make the tech news websites.

At least with Gmail, it appears that there are backups in place and are being slowly restored.