It looks like users are experiencing some downtime to multiple Microsoft services, for the last few hours and counting. Hotmail is one of these services, and three hours without email is like a week without snail mail for some.
SkyDrive and Outlook are experiencing similar issues, with SkyDrive users having problems with file editing. Hotmail and Outlook issues seemed to be pegged on an issue not displaying all of your emails, which is, well, quite important. Microsoft have given the following statement on the problems:
Microsoft is investigating an issue affecting a small number of customers' access to Hotmail and Outlook.com, and we are working to restore full access to the service as quickly as possible. For the latest information, we encourage people to visit the Hotmail and Outlook.com status page (HTTPS://status.live.com/).