It's official, straight from the Windows Live Blog. Your Hotmail issues have now been resolved. For those of you that missed it: from 30 December 2010, 17,355 Hotmail accounts were impacted when the Hotmail servers failed to correctly balance server loads – put simply, those users temporarily 'lost the contents of their mailboxes'. The messages weren't 'lost' though, and all affected users have had their emails restored as of 2 January 2010.
Microsoft claims that they're still investigating the cause of the issue and has yet to explain the outage. The outage itself seems to have caused a PR headache for Microsoft, considering the small amount of impacted accounts, with the BBC and other news agencies picking up the story. Additionally, affected users used Facebook and Twitter to vent their frustrations, making the problem appear more widespread than it was. Microsoft has again apologised to the affected users and businesses, and state that they're working to ensure that it doesn't happen again.
Microsoft has been working hard in recent years to increase the capabilities and stability of its online services, including Hotmail. As Google and Microsoft really begin to battle in the software as a service space (Google/Google Apps versus Office Live/Windows Live/Bing), issues like this are likely to damage business confidence in the company's online offerings – perhaps to the benefit of its much-loved competitor. Currently, Microsoft's Hotmail is the second most visited webmail site in the US (behind Yahoo), with Gmail receiving around half the traffic of Hotmail.