I spotted it again today on Jerry Coyne's blog and when reading through the comments noticed that a helpful pedant had pointed out a gramatical error in the advert. Once I had noticed the error it became extreemly infuriating, so I've had to edit the orginal image to correct it.
I guess it's to late to replace the original image now as it has escaped the confines of my blog, and it's old news now anyway, but if you do still link to or tweet the image it would be most appreciated if you use the corrected image. Partly so I don't get annoyed every time I re-read my original gramatical cock-up but mainly because I've now stuck my name on it.
Much obliged, Crispian.