I'm just guessing here, but if you write a textbook and get published by a traditional publisher (McGraw-Hill, etc.), they probably disallow you from creating a copy of that same book and selling it for $5 from your own marketplace. They check it for quality, help create the physical book, and put their name on it. They even have some ownership. I'm simply seeing Apple as a publishing partner here. They're helping you create the book and distribute it, and with that agreement you're bound to certain limitations, such as a percentage they'll take for distribution (surely less than what a traditional publisher would take).
You can play the slippery slope card all you want, and try to apply what we're seeing to all other applications, but I don't see anything to back it up.
Regarding remote wipe. I have no idea if that's in the iBookstore EULA, and haven't found a thing about it. My guess is like apps, you'll have to confirm and download the update yourself. In fact, when apps are taken off the app store, you still get to keep them, whereas Android apps have a kill switch. Have you seen anything that implies remote wipe capabilities?
As an iOS 'fanboy' i have to tell you that both iOS and Android have a "kill switch". It's a measure for the really dangerous cases and Google has used it once or twice, and i guess Apple too (not shure atm). When jailbroken, you can turn it off on both platforms.
But you are right in that there seems to be no such thing for books, unlike on Amazon (remember the 1984 case?)