where the writers are
Fortune-Cookie Tips for Writers, #280

Every time I think we’re done discussing blurbs, I get sucked in again: It is never a good idea to say in a request for a blurb, “Hey, I know you blurbed so-and-so”; trying to guilt an author into helping you because they helped someone else is not the way to go – you need to make the case for why you and your book are worthy of help.