Neil (I'm allowed to call him Neil, I did an event with him at Waterstone's once, Dave McKean was there, he lives nearby and I used to give him random discounts afterwards, but he always looked at me like I was mad*) asked in his blog for people to put this link in their blogs as part of a plan to freak out Penn Jillette that I didn't really understand.
* see also the me and Matt Begins-With-a-C's interesting but ultimately corrupt 'random ten percent discounts for pretty girls' experiment, which lasted until we were found out.**
** Two years later.
UPDATE: just to clarify, if anyone from Waterstone's security department is reading this, 'Matt Begins-With-a-C' isn't the one you're thinking of, he's a different one. And he's dead now, anyway. So let's all move on.
Sometimes I forget people I know still have proper jobs.