That's not really true. Apple faced two pressures which forced them to drop DRM from their music store: (1) Amazon MP3 who used lack of DRM as a point of diffe

That's not really true. Apple faced two pressures which forced them to drop DRM from their music store: (1) Amazon MP3 who used lack of DRM as a point of differentiation over Apple and (2) the threat of regulatory action in Europe due to lack of interoperability. Amazon today is in the same position in terms of ebooks as Apple was with music at the time - it uses DRM to lock customers into its hardware product, in turn driving further purchases towards its own store. This may or may not be a revenue-maximising strategy for them but it certainly looks like a market share-maximising strategy. Apple is also in a similar position again trying to drive purchases to its own store. At the same time, regulatory action on competition has been more focused on contractual terms and price collusion/fixing than on interoperability; regulators will probably want to wait a while after sorting that mess out to observe whether they see competition acting effectively or not before addressing interoperability in ebooks. For the same pressures and reasons to cause DRM to be dropped from ebooks, I think it will take an outside competitor (probably a new entrant) without a significant stake in hardware AND with substantial buying power to break this cycle. I can't think of an obvious candidate to do this today but perhaps I'm missing one.