Browsing the wikipedia I came across this little tidbit about Hotmail:

On 24 December 1999, MSN Hotmail, the free web based email service owned by Microsoft, became inaccessible for a couple of days when the domain name registration lapsed for passport.com - which Hotmail uses for user authentication.

The registration fee for the expired domain was paid by Hotmail user Michael Chaney on December 25 as a Christmas present to Microsoft and the 20 million users that were unable to access their mail.

Microsoft confirmed to Chaney a couple of days later that his $35 payment to Network Solutions did in fact solve the Hotmail outage problem. As a reward for Chaney's quick thinking and generous move, Microsoft sent him a check for $500 and a copy of Visual Studio 6.0.