According to the Facebook statistics page [0], there are over 400 million users on the site. The same page states that about 70% of those users are from outside the US. That suggests that 30% of Facebook users (about 120 million) reside in the US. Let's assume that the entirety of her fan base is within the US. That means her fans only represent (at the _most_) approximately 5.59% of US Facebook users. I wish I had data per state so I could pin this down more thoroughly (wrt to ratios of Megan Fox fans to state populations), but going on just what I have seen so far I am admittedly suspicious of the gentleman's data.