Google's strategy is clear. Play Services has system-level powers, but it's updatable. It's part of the Google apps package, so it's not open source. OEMs are not allowed to modify it, making it completely under Google's control. Play Services basically acts as a shim between the normal apps and the installed Android OS. Right now Play Services handles the Google Maps API, Google Account syncing, remote wipe, push messages, the Play Games back end, and many other duties. If you ever question the power of Google Play Services, try disabling it. Nearly every Google App on your device will break.
Fragmentation addressed through the backdoor. Too bad it's too technical for most blogs, so the fragmentation line will be parroted for years and years to come.