Some time ago, both Twitter and Drupal went offline. They had scheduled planned maintenance, but seemingly for two different reasons. I suspect Twitter again had too many tweets. It's a phenomenon that is happening rapidly. People seem to use Twitter a lot, increasing its server load. But in Drupal's case, it was doing an upgrade from Drupal 5 to Drupal 6.
Whatever the case may be, down times are important. Servers, or at least clouds, work 24/7. Given the load that is bombarded into them, all loose ends need to be tied once in a while to make sure they don't crash.
