Some of the examples cited:
Adverbs describes adolescence, friendship, and love with such freshness and power that you feel drunk and beaten up, but still want to leave your own world and enter the one Handler’s created. Anyone who lives to read gorgeous writing will want to lick this book and sleep with it between their legs.
David Eggers, blurbing Adverbs, by Daniel Handler
The brilliance of Barker’s style is beyond perfection.
The London Spectator blurbing Nicola Barker’s last novel, Clear by Nicola Barker
Does anyone really buy a book because of what the blurb said? Granted, if a favourite author has blurbed "This didn't suck too badly," I'm less likely to buy the book. But, in general, if an author I trust has endorsed a novel, I may pick it up, no matter what the endorsements says. If I've never heard of the blurber, then the blurb is unlikely to grab me, no matter how many adjectives it uses.
And, of course, all blurbs are positive, and most wax rhapsodic. So how valuable is the tool, or do we just use them because the book would look naked without?
I'll give George Orwell the last word: “when all novels are thrust upon you as works of genius, it is quite natural to assume that all of them are tripe.”