Apple denied claims that it was keeping tabs on its customers, saying the file records Wi-Fi hot spots and cell towers in the general area of iPhones, not the whereabouts of their users.
The company implied that the privacy concerns raised by that file were partly based on a misunderstanding. But it also said that a software error was the reason the files are storing up to a year's worth of information, and that it would fix that issue and others in a few weeks.
http://news.yahoo.com/s/ap/20110427/ap_on_hi_te/us_apple_iphone_tracking