Big internet sites make the economy more efficient. But the problem is an efficient economy doesn't need workers. And if there are no workers, there's no one to purchase the goods.
"Workers" can find something else to do, possibly newer and more interesting kinds of work, or possibly less work on a four day week, etc.
Look, humanity is stuck on this rock, we aren't going anywhere unless someone figures out how to do the impossible and fly around the galaxy faster than light. So our society needs an eventual end goal, and it seems widely agreed that this end goal should be that we all live lives of leisure and can do/go/explore/build whatever the hell we like, whenever we like it. Obviously along the way that means we'll end up doing less and less work until hardly anyone is doing any real work at all and it's all done by robots a la the world of Manna which was discussed here on Slashdot not that long ago.
So if books get delivered by radio to a device with a battery that lasts for a month and gives me access to the whole world's library for a pittance, how is that not a giant step towards the kind of utopia I described above? Small local bookshops staffed by smart shop assistant girls with cute French accents are great until you realise they don't have the book you want and you had to haul your ass into town in order to discover this fact (assuming the shop was even open by the time you got there). It's not something I would trade progress for.