this is a really good question, one that you have presumably answered yourself with your tags.
that said, here are the possibilities that i can see:
1) they were forced to do something along these lines by some legal recourse taken by either keith herself (the pie-ee), the cops, or her publishers (perhaps regarding insurance for the space, or some such bureaucratic nightmare)
2) it's a prank post by someone unrelated (and has yet to be noticed by any of the bookfair organizers who could refute it)
3) it's a post by one of the bookfair organizers who perhaps likes keith and got carried away and is too proud to back up now
4) it's fucking stupid and there is no excuse for it
5) all of the above