John Scalzi has smart things to say about Dan Brown in particular and uber-popular authors in general (it’s the part after he talks about his book tour, obviously).
Pullout quote, although you should really go read the whole thing:
Being cranky about a Dan Brown book not being high literature is like yelling at a cupcake for not being a salad; it’s really missing the point. You don’t want the cupcake? Don’t eat the cupcake. Apparently lots of people like cupcakes. They don’t care that you want them to eat salad. You eat salad, if it’s so important to you.