@muzel-e
I went through the painful process of trying to delete the recipient history one-by-one and at first this seemed to work but guess what; after a complete erase and setting up the device as new THE PREVIOUSLY CONTACTED ADDRESSES AND CONTACTS REPOPULATED AGAIN!!!
Furthermore my "previous recipients in Mail in OS X have AGAIN repopulated. So not only do Apple make it extremely difficult to delete the tracked information they seemingly keep the information on their servers even after you've tried to delete it and it keeps repopulating. Apple only seems to delete the information from being visible on the devices you've attempted to delete them from. In other words APPLE IS TRACKING EVERY SINGLE ADDRESS AND NUMBER YOU EVER CONTACT and they refuse to let you delete the information. This corroborates other posts above that report similar situations where the information comes back even after you've tried to delete it.
This is shocking behaviour from a company that supposedly says they care about our privacy but really they're just pawns of the government and iCloud tracks everything about your activities. Remember when it was discovered that location history was stored in the device? Well, even if they made that harder to find or turned it off from being available on the device I bet that information is still tracked, sent and stored on iCloud.
The bottom line is I don't trust Apple anymore.
I am going to call AppleCare and complain but fat chance they'll change their routine data collection services because of a few complaints. The only thing you can do to prevent this tracking is turn off iCloud and refuse to sign in, thereby missing out on iMessage and other services including iCloud mail. It's a shame that Apple is behaving this way but I value my privacy more than a few internet services. I'd rather use services that are secure and that don't track and store usage information.
I also encourage anyone concerned by this to read about recent revelations of hidden services in iOS that collect and send information to Apple. http://arstechnica.com/security/2014/07/apple-documents-previously-undocumented- services-that-can-leak-user-data/