Gartner makes the observation that…
"Every time a user downloads a native app to their smartphone or puts their data into a platform’s cloud service, they are committing to a particular ecosystem and reducing the chances of switching to a new platform"
I wrote about how personalisation influences loyalty as long ago as 2005. At the time it was in the context of network operators. Since then, Apple and Google have siezed this opportunity.
Apps are mostly replacable across platforms and I think cloud services are a more compelling proposition to influence loyalty. Google has an advantage here as they are able to offer free cloud services while Apple changes $99/yr for its MobileMe services. As I previously speculated, in the iOS vs Android end game, income from cloud services might become more important for Apple.
Aside from Google and Apple there are still opportunities for 3rd parties, such as network operators, to provide their own, more vertical, services in order to retain their slice of customers. Google and Apple have to provide cloud services to very large numbers of people and this, in itself, limits the number and kinds of services that can be offered. Smaller scale, more specialised, focussed services can better meet end user needs and provide deeper, sticky services.