Some Hotmail users have had the contents of their inboxes completely wiped, thanks to what is thought to be a date bug.

Users logging in were greeted with a completely sanitised inbox and new-user welcome screen, similar to what those who haven't used the service for 270 days see when their data is summarily deleted.

Microsoft claims to have fixed the problem and restored the emails, but it's been a worrisome few days for many users. Hotmail is the world's most popular web-based email service, with 364 million users. Although figures have not been released about how many were affected by this issue, nearly 500 people posted complaints to the Windows Live Solution Center. That's 500 users who bothered to complain, or know how to do so.

Bearing in mind that Hotmail is a service used by many technically illiterate users, the total number of those affected is likely to be huge. If only one percent of Hotmail users were affected, then 3.6 million annoyed individuals were hit.

Microsoft responded in fire-fighting fashion, claiming this was a "limited issue" and apologising for the inconvenience. Users might well feel despair at such a pathetic excuse. The problem arrived at a particularly bad time for Microsoft, which will soon launch Office 365, its first major attempt at a cloud-based office suite. If Microsoft can't reliably maintain a cloud-based email service that it's owned since the last century, is it safe to trust the company with business data?

Although Google or alternative web mail providers could capitalise on the slip-up, they'd be advised not to throw stones from houses made of glass. A significant number of Gmail users have seen their entire inbox disappear from time to time. This happened to me last year. I've been a Gmail user since 2004 and, although my messages reappeared on the next login, for about 30 minutes I felt like a one-ton weight had fallen on me. I felt I'd lost a significant chunk of my life.

As is the way for many people, Gmail is a mirror of my life. For example, Gmail acts as a backup for family photographs, in the form of emails I've sent with them attached. If I forget somebody's phone number or address, I search for the email they sent me years ago containing the details. I even send myself messages containing stuff I need to remember.

I know it's foolish to rely on Gmail in this way, but I'm also human and therefore lazy. Several times I attempted to back up everything using Google Gears but it never worked properly, and it has been discontinued.

We have to hope that Microsoft and all cloud providers learn lessons from this crisis. They must understand that every single user is precious. We are putting an insane amount of trust and expectation into their hands. A reliability rate of 99.99 percent isn't good enough; it has to be 100 percent. If this can't be achieved, then cloud providers shouldn't bother.

This isn't necessarily a requirement for other online services. If Facebook goes down, for example, it can be irritating but not devastating (unless you're a teenager, I suppose).

However, services such as cloud office suites or email platforms are different. They're lifestyle services in a very real sense, because we manage our lives around them. We trust them in a way that we've rarely trusted computers before, and this is going to get more intense as the cloud extends to our phones and tablet PCs. Cloud service providers need to ensure they don't betray the faith we have in them.

See also: Hotmail back online after hours-long outage