So umm no mention of the 4chan DOS attack? I mean, not that I hang out there or anything, but a friend told me that they organized an attack. You'know. Jus sayin. /b/ye
The more likely explanation is that someone on 4chan noticed FB was down -- and then started talking about DOSing it.
After facebook's outage started, there were like 9128 threads in /b/ with trolls claiming it was their success.