I made a little fuss about these stats on Twitter already, as I couldn't really believe it when I first saw the infographic. But upon further discussion on the topic in the WarcraftPets forum, I've become fairly disillusioned with the whole thing.
There are three main questions that should have been answered from the get-go: What data did Blizzard use, when was the snapshot of this data taken, and what was the criteria for "rarest" pet?
Without answers to these questions, it leaves players like me in the dark and scratching their heads. The data just doesn't match up.