The digital grassy knoll set's collective head is about to explode. Apple is collecting iPhone usage data, linked to the user's specific personal information. Apple gathers that personal information when you sign up for an iPhone, and may be doing something or nothing with it after associating it with your usage data. People's opinions on this seem to depend on the ratio of Apple fanboy to paranoid privacy nut you are. If you're 100% both, this is bad news:
From this information, Apple could build a profile on users. Where they travel, where they spend their free time, where they work, where they invest their money, what they browse, etc etc. Obviously most users would like to be able to control who has access to this information. If they connect this data with the credit card that you used to purchase the iPhone (remember, you can't use cash anymore), they could build an even bigger profile on you.
Unfortunately, it doesn't look like you can doanything about it - though hackers are working on it now. According to Uneasysilence.com, if you use an iPhone, you've already forfeited this right to privacy (from the Apple Terms of service)
Of course, many of us have already built our own "profile on iPhone users." They appear to be persons with $600 more in their budget for a telephone than we have, and they worry about people spying on them all the time. They must be secret agents or ninjas or something. Cool.