Hey Apple, why don't you get to studying on good old Lotus Notes? Multimaster, highly replicated, non-relational, conflict-reconciling, document-focused storage for what, twenty years?
I assume you know that Lotus Notes was basically just a sync engine. That was its one and only core feature [1]. Apple is overextended - they have to keep up with Android and maybe even WP8. To fix iCloud CDIS with application-specific arbitrary data models is a very difficult task. Especially with their dumb master approach. A true client/server solution requires a smart server to mitigate and handle sync conflicts. As users demand more and more functionality, including offline capabilities, iOS apps begin to morph into client/server ptograms. So much so that what most developers end up doing is writing their own client/server sync. iOS and Android budgets dive into the deep end once sync requirements get baked in.
[1] http://www.ibm.com/developerworks/lotus/library/ls-NDHistory...