If you downloaded the Facebook app for your mobile device, and just zipped through the install options (like users commonly do), did you know all your contacts could now be on your Facebook Contact list (formerly Phonebook) and can be datamined by Facebook? This is also disturbing if Facebook itself gets hacked and your phone contacts get stolen, giving significant access by malcontents to personal information about you and your contacts. Also, it would provide a larger incentive for bad actors seeking to harvest and sell your personal information to the highest bidder, now they’d have even more of your information (and others) in one fell swoop. Note that Facebook says the Contact list contents aren’t necessarily publicly visible, stating, “Just like on your phone, only you can see these numbers.”
If you choose later to opt out of having your mobile device phonebook sync’ed, you wouldn’t be alone. The forums are rife with users trying to figure out how to easily disable the sync function on their specific mobile device. Some have even resorted to removing the app altogether and re-installing it without the feature enabled, some just give up. Clearly, steps could be taken by the Facebook mobile team to make it easier for the user to opt out later, though some suspect this is by design. After you manage to disable the sync feature on your device, you also would have to disable it on the Facebook.com site under your account. To do that, you can visit:
Account -> Edit Friends -> (Mobile graphic) Contacts
Then follow the link on the right side:
Which will lead you to a page like:
Notice there is a reference to an iPhone, which wasn’t used in this example, but no reference for how to do it on the device that was used. Also, notice the bit about friend suggestions becoming less relevant if you opt out? This means their algorithms would know less about you, so could predict with less precision who you might also want to friend. Advertising harvesters use similar language when attempting to target marketing efforts, and there’s no small amount of business to be had feeding increasingly accurate information to a prospective high bidder.
ESET Research Systems Manager