How Facebook integration with iOS/OS X works

When Apple (s AAPL) announced a system-level integration with Facebook (s FB) this morning, I uttered a silent groan and cursed under my breath. On Twitter, I was more polite. “Not so thrilled by the Facebook integration into the new IOS 6.0. I wonder what are the privacy precautions to deal with Facebook,” I wondered out loud.
I just don’t want Facebook constantly tracking me and I don’t want any information leaking especially on my iPhone. Perturbed, I tried to get more details on the integration from Apple. Here is what I understand about how it works – when using the system-level single sign-on, when you want to share something via Facebook, the system logs you into Facebook, shares whatever you want to share — a link, a video, a photo or whatever — and then logs you out.
You still need to go to the browser to login to Facebook (if you don’t enable auto-login). The contact and calendar data is shared only after you approve the sharing and also is a process that doesn’t allow constant sharing. In addition, there is no information being leaked from the system, I was assured. Apparently this is also how Twitter’s system level integration works.
However, despite all those assurances, I feel a little queasy by this partnership. I think am just going to skip the whole single sign-on option – I simply don’t trust Facebook. As someone on Twitter said: “Its an ideological mismatch: one company cares about users vs the other doesn’t. FB’s founder/management are careless w privacy.”