[koudi]

True, although such strict lock-in seems to be counter-productive. For example - I have iPad (and love reading on it), but I never buy books on iBooks Store. I use amazon instead, because I can easily strip DRM and convert to any format I want and read anywhere I want (should I ever buy different device). iBooks books are tied to apple devices for ever.

This strategy may work for now, but I don't think it's viable in a long term and apple always seemed to prefer bigger picture rather than pursue immediate profits.

[cremnob]

It is long-term. Opening up iBooks to any device or just being available on the web would increase profits immediately. Building out the ecosystem is the long-term part.