Stephen Dubner asked this question after he'd received a request to write blurb for an upcoming book. I'd read Freakonomics after the NY Times piece. To answer his question, if it's a blurb by someone I respect, I'd be more likely to pick up the book. Provided the blurb indicates why the blurb-er liked the book himself/herself and doesn't use stock quotes like, 'A page turner' or, 'A must read.' Blurbs won't work if the blurb-er tells what readers will like. Readers don't like being told. I used to make that mistake when I wrote reviews, almost always ending with "You'll love it!" I can imagine someone reading them and instantly thinking: "Oh yeah? Fuck you, Miss Cleo." I know better now.
For example, I'd be more inclined to pick up a book if Stephen J. Dubner wrote:
"This book opened my eyes to the world of numerology and its impact on the future of Wall Street"
as opposed to:
"An eye opener! If you love numerology and Wall Street, you'll love this book!"