Satya Nadella made a parallel observation that operating systems have moved off of particular hardware (e.g. running Windows 95 on your PC) and into more of a consistent interface for interacting with all the devices in our lives, thus Microsoft Office's transition to a cloud service (and his general push for Microsoft to become more serious about the cloud).

Even though I don't care a bit about brand loyalty, I can definitely see the appeal of every device (PC, phone, car, TV, eReader, watch, whatever) all sharing the same abstract "operating system" interface, sharing your preferences, schedule, etc without the user having to even think about syncing this information.

There's obviously a lot of appeal to a corporation to have this data as well, but even those of us who are opposed to the corporate abuse of data have to acknowledge this is the future. I'm optimistic that an open-source self-hosted solution can accomplish the same thing, but I'm not sure one actually exists yet.