I don't think so. Facebook only had 132M unique visitors in March, compared to 400M users they are believed to have. To say that 400M were active last 30 days,

I don't think so. Facebook only had 132M unique visitors in March, compared to 400M users they are believed to have. To say that 400M were active last 30 days, Facebook need to workaround the pigeonhole principle.