NPR reports that e-booksellers are allowing writers to see what parts of e-books readers are responding to. They talked with a couple of novelists about this idea, including Seattle's own Jonathan Evison:

"I'd be lying if I said I wasn't thinking about the reader all the time. I always think about the reader," says Evison. "I'm trying to create an effect for the reader, and sort of engage them in a sort of collaborative dance ... But I'm still trying to be the leader...Moby Dick is one of my favorite books, but let's face it — it's a hot mess," says Evison. "If I had software that said, 'Look, maybe this four-page essay on scrimshaw isn't gonna fly with your 28 to 40 male [demographic],' what would we have lost with that? Sometimes, you know, it's just got to be a little bit of a dictatorship."

Evison doesn't speak for every author when he says he thinks about the reader all the time; I think as a rule of thumb, the more literary an author gets, the less likely they're willing to admit to that. And I'm sure that one day, there will be another distinction between the commercial authors who admit to tailoring their books to market research, and those who don't.