Writers who blurb a ton of their friends' (or acquaintances') books are known as "blurb whores." That's not necessarily a bad thing! But every time you blurb a book ("Outstanding! Brilliant! A tour-de-force.") you should definitely change the wording around—or change the actual words! This makes it look like you've read the book. Arianna Huffington of the HuffPo forgot to do this, as Portfolio's Mixed Media points out. The phrase that was so nice she used it twice? "Fierce, funny, disturbing.... ultimately uplifting."