Blizzard DDOS Attacks End

A tweet from Blizzard CS reveals a denial of service attack knocked and Blizzard online services out: "We're currently investigating an issue affecting our authentication servers, which may result in failed or slow login attempts." Perhaps this was someone taking advantage of advance warning that support is short staffed for the holidays. In any event, things seem to be cleared up now, as the latest tweet on the topic says:
The DDOS attacks that we were monitoring have ended. If you are still unable to log in try

Connection Troubleshooting - Blizzard Support.