We have one so far.<p>Let's see how many comments we can get explaining why this was bad when Microsoft did it with IE but just fine when Apple does it with iBooks.<p>Bonus points if you somehow spin embrace-extend-destroy as a good thing by conflating what's good for the users with what's good for Apple and its shareholders.
Most companies are using the open standards of the web and using them to build their own closed standards. Apple isn't the only one, Amazon et al are as guilty as everyone around. Hardware lock-in from the previous decade has now moved to content lock-in on the Internet.
This is a false dilemma. Authors don't have to use iBooks software to author ebooks and users don't have to use iBooks to read ebooks on the iPad (and they probably don't because it's really buggy). Problem solved.