Amazon's share of the ebook market is expected to fall dramatically over the next five years, with figures of 90% down to 35% suggested:
Above I actually said "an industry standard" rather than specifically saying Adobe, but I'll argue the point anyway. Adobe Adept has become the de facto industry standard, in that the vast majority of bookshops are using it, as are public libraries. The fact that the Kindle format currently enjoys more sales doesn't alter that. It's not a standard if it is tied to one sales outlet.
We all want DRM confined to the dustbin, except presumably for library loans, but given that the publishers are insisting on DRM, as Tamara notes, it is irritating - for iPad owners - that Apple chooses to slap yet another variant on their books. People who don't own iPads have their choice of store reduced by one (one that doesn't yet exist), so not too big a problem. iPad owners will need to have multiple apps to read their books if they choose to use both their own Apple store and the majority of other shops.
Stustaff's point about the cost is a good one - I hadn't realised just how much Adobe were charging - but Apple will still have internal salary costs to maintain their Fairplay DRM for books as well as movies, and deal with the book-specific issues.