Hm, although an opt-out option might seem a reasonable request, Apple has to draw a line somewhere. If you want to have fast and accurate positioning, you have to provide them with your anonymous tracking data. That's the tradeoff, which I think is also reasonable to most people.
(I wish Apple would take that same stance with regard to crash logs. If you want stuff from the App Store, you have to let iTunes send your crash logs to the developers, without having to ask for permission first. There really is no good reason why anyone would need to opt-out of that.)
"If you want to have fast and accurate positioning, you have to provide them with your anonymous tracking data."
No I don't have to.
I am currently working on an offline positioning system based on a (hopefully complete) dataset of all GSM-Cells in the world (http://myapp.fr/cellsIdData/). The sqlite3-database is currently 25MB big with some room for optimization. I do this for Android but the iPhone also has enough space to hold this data. Although I think it would be impossible with iOS because of missing APIs to be notified when the cell tower changes.
I'm sure that cell towers are enough for Assisted GPS to get a quick fix.
If people would have found a data set of all cell towers ids and coordinates no one would have had concerns about privacy.
Tracking data is only anonymous if it cannot be de-anonymized. Since I cannot check that this is not the case (with Apple, Google and Skyhook) I have doubts about the so called anonymity.
edit:
I am looking for a comprehensive dataset of wifi access points MAC-adresses and coordinates
I should've been clearer: I didn't mean "have to" in the sense of "strictly technically necessary" but more along the lines of "if you want to use this functionality, you'll have to help us out by collecting the data that'll make it work better for everyone".
Whether or not the collected data really makes the positioning that much better, I don't know, but Apple apparently seems to think it does.
(I wish Apple would take that same stance with regard to crash logs. If you want stuff from the App Store, you have to let iTunes send your crash logs to the developers, without having to ask for permission first. There really is no good reason why anyone would need to opt-out of that.)