I looked it up and it said something about January 28th, they are going to.
"The YouTube video threatened a January 28 attack, going so far as to include in its description a URL for downloading a program that would reportedly enable users to crash the social network's servers."
But the attack wasn't scheduled until Jan 28th..
But on Anon Twitter, not sure if it's legit or not, but they say "#Facebook.com is NOT under denial of service attack. STOP LYING." which seems very odd...