I know that there's mention of this date in another thread I started here, but I wanted to draw attention to it.
We lost 50% of our traffic on Tuesday, November 20th, 2012, and haven't recovered since. That day I don't believe lines up with a Google Panda algorithm update (which we were hit by and recovered from in the past). I got some confirmation that other forums were hit on the same day as me.
Does anyone know what happened that day? Any feedback appreciated!