B&M book stores were disappearing long before the iBooks store thanks in no part to Amazon and other internet traders. Amazon selling ebooks below cost certainly played a part in that.
The music industry only exists as it does now thanks to iTunes. Piracy levels have fallen dramatically (much to the chagrin of the RIAA) as new owners of digital music devices have a legitimate method of purchasing digital content.
The record industry left to it's own devices and pricing and multiple DRM'd stores was not working.
The publishing industry left to their own devices and guided by Amazon was facing the same abyss. Imagine how many independent authors would have received a chance to enter the market under that model.
Apple have even supplied the tools for writers to create and publish works.
What was Amazon's plan? Oh, that's right... pilfer existing authors from the existing publishing houses. Really innovative