Knowing advertising and the E-world, I am sure it would be people like Amazon, Yahoo, and God only knows if you get the big e-advertising agencies in there.
I am sure they would want to advertise at the beginning, the end of each chapter and at the end.
It would probably be worse than TV is now. I counted 14 commercials on a hard break (on the half hour) of a show the other week on TV. Twenty minutes of every hour program is now commercials.
This is among the reasons I don't watch network television anymore. They used to present commercials to us as the cost of "free" television. If they had no sponsors, they couldn't afford to put on the shows. Now they're dropped that pretense, and it's obvious they want to put on as little show as they can get away with and still keep you around for the commercials. If they thought we'd just watch commercials all night, the networks wouldn't mess with shows at all.
It's like Al Swearengen said in DEADWOOD: Sometimes I wish we could just hit them over the head, rob them, and dump their bodies in the creek. But that would be wrong.