A different angle: like with some previous comics, this one seems like a general attempt to make an easy joke that stat people will like, print, cut out, and put on their walls. "A special xkcd, just for me!" they will think. Please: do not blindly e-mail this comic to all of your friends who use statistics. It is annoying. It is not nearly funny enough, or faliing that obscure enough, to warrant spreading like beer pong herpes.
My heartiest laugh that was correlated to (and caused by) a comment about correlation and causation was when Nate Silver was debating John Zeigler on some dumb online tv-type show. The conversation went something like this:
JZ: But 75% of the people who heard [X] voted for [Y]!
NS: Ok, but that doesn't mean they voted for [Y] because they heard [X]. You of all people should know that just because two data points are correlated doesn't mean one caused the other.
JZ: But with numbers as high as 75% ??? Come on!
This made me laugh, because JZ was being a giant idiot. You can have as much correlation as you want and it still can mean nothing. ha ha, stupid people.
From nowhere: I find that God's eyes blinking on this Overcompensating freaked me out. A comic like that, that is just about always static, should stay static. This is crotchety-old-man me speaking, but I just think it's weird. (this dinosaur comic is a little better because the movement is so obvious, it doesn't sneak up on you all of a suddent)
update: See how up there I predicted that statisticsy people would spread this comic around to all their friends because hey, look, it's a statistics comic! ? Yeah well I was at least a little right: Noted smart person Steven Levitt has apparently broken his "no cartoons" rule for the very first time to bring you you-know-what. curse you, levitt!