The cloud has failed roughly 150,000 Gmail users, whose e-mails have been deleted and accounts disabled by a mysterious glitch.

Users on Google's help forum report that the Gmail bug responsible deletes everything, including e-mails, labels, folders, and settings: http://www.google.com/support/forum/p/gmail/thread?tid=3064c61f77cd0f46&hl=en
When affected users log on, they see a welcome message as if they've never used Gmail before. Other users simply found their accounts disabled while repairs are being done. According to Mashable, the bug affects less than 0.08 percent of users: http://mashable.com/2011/02/27/gmail-glitch/

It's not yet clear whether Google will be able to restore the deleted e-mails. Google hasn't addressed the issue on the official Gmail blog: http://gmailblog.blogspot.com/ , and the Google Apps Status Dashboard only acknowledges an ongoing "service disruption": http://www.google.com/appsstatus#rm=1&di=1&hl=en
Eventually, Google will have to explain how this happened and what will become of affected users' accounts.

For everyone else, the lost e-mails are a reminder of how Web storage isn't completely immune to failure. If you rely on Gmail to safeguard e-mailed documents and important correspondences, consider backing up your account.
Backup Advice

PCWorld's Ian Harac reviewed Gmail Backup in December and found it to be a functional, but feature-barren option. The software is free, but right now I can't access Gmail Backup's Website: http://www.gmail-backup.com/ (Perhaps it's overwhelmed by demand.) Ian also recommended Gmail Keeper, which offers multiple profiles, scheduled backups, and account migration for a one-time price of $30.

If you're comfortable backing up Web-based e-mail to another Web-based service, Backupify routinely saves Gmail accounts and other services such as Facebook and Picasa to its own servers: http://www.backupify.com/
The first 2 GB are free, and premium plans costs $5 per month for 20 GB and $20 per month for unlimited storage.

The lost e-mails are reminiscent of a Hotmail server problem that temporarily deleted the e-mails of more than 17,000 users in December. Microsoft was able to restore access a few days later, so maybe there's hope for those unlucky Gmail users.

Updated With Google Response:The Next Web reported: "A very small number users are having difficulty accessing their Gmail accounts, and in some cases once they're in, trouble viewing e-mails: http://thenextweb.com/google/2011/02/28/google-acknowledges-gmail-issues-as-users-complain-of-missing-emails/
This is affecting less than .08% of our Gmail user base, and we've already fixed the problem for some users. Our engineers are working as quickly as possible and we hope to have everything back to normal as soon as possible. We're very sorry for the inconvenience."

(PCW)