People who stick price labels on to the front of paper dustjackets.
A tip - to remove the price from a glossy modern jacket use a bit of lighter fluid - the sticker will lift clean off.
Paper jackets though are a different matter because invariably, the paper will absorb some of the glue leaving a residue, or in trying to remove the sticker some of the jacket will come off with the sticker leaving a little white patch.
Even auction houses, who really should know better do this. Sticking their great big lot numbers on to lovely old book jackets. So if you love books, don't do it.
Ok rant over - as you were!!