I have a short theory on what promotes access to user data. If a data collector has good intentions in that it appears focused on helping me rather than third parties, and this is reflected by secure systems and processes, then I'm more likely to trust it and give it access to my data.
Conversely, if a data collector has bad intentions in that it appears focused on helping third parties as much as helping me, and this is reflected by less secure systems and processes, then I'm less likely to trust it and give it access to my data.
I believe this phenomenon may be playing out with Apple and Google/Android. Many Android users are currently giving Google tremendous access to their data, but as they're tracked and bombarded with ads, and they become more aware that Google is focused on serving both end users and third party advertisers, they may become less willing to give Google access. This trust problem is magnified by Android fragmentation and the difficulty of keeping Android secure.
As users become more sophisticated/educated about the use of their personal data, it seems likely that good intentions (prioritizing end users instead of third parties) and secure systems/processes will be needed to create the trust needed for smartphone makers to continue collecting user data.
Companies that create user trust are in the best position, over the long term, to collect the most relevant, valuable user data. Because trusted companies are in a better position to gather relevant user data, they may also end up with better intelligent services (whether it's Siri or Google Now).
One other point: it's been argued that people will give up some measure of privacy/security regarding their personal data in order to obtain better intelligent services (like Google Now). I'm not convinced of this -- to me this is like arguing that I'll trade away the security of a bank account for the greater convenience of hiding cash under my mattress. And why would I trade away privacy/security if there's a smartphone maker I trust that can protect my data while still giving me more than "good enough" intelligent services (a la Apple)? I know I sound too much like an Apple fan.
The author owns stock shares of Apple.