blurbs: how effective are they?

I pick up the latest paranormal on the "what's hot on Young Adult" table, turn it over to give the summary a try and spot the blurb promoting the novel. "Unputdownable!" it gushes, and I start to let a little hope grow -- until I see it's another blurb from Becca Fitzpatrick.

And it's not even that her books are bad (I haven't read the Hush, Hush series); it's just that she blurbs everything. So does Lauren Kate. So does Meg Cabot. After a (very short) while, their effusive praise loses its impact. It's as if these paranormal authors feel a need to

• promote their genre,
• get their names on as many books as possible, or
• be indiscriminate in terms of taste.

Or maybe they actually like the book. One can hope, right?

Okay, so now that I've denounced blurbs (and probably offended a couple of people -- sorry about that), I want to hear what works for you in terms of blurbs. Is it the author's own books? Does writing skill guarantee good taste? Is it what the blurb mentions -- a pragmatic heroine, a vivid world, gorgeous prose? Or do blurbs not sway your decisions at all?