Mac: If the news that some apps may be scanning and harvesting your address book has you disturbed, AdiOS is a Mac app that looks through the iOS apps you have synced with your iTunes account and alerts you if one of them is known to upload your addresses to a third party.
AdiOS suggests you delete any offending apps that harvest your address book this way, but some of them make sense. For example, Angry Birds frequently shows you top scores of your friends, and many other mobile games on iOS and Android both use your contacts list to enhance the game, either by adding characters based on your friends or by connecting you to other people you know who play the same game. Social networks almost always access your contacts list to connect you to other members. Even so, the app gives you the power to decide which apps should and shouldn't have the right to dig through your addresses, and make an educated decision as to whether you want to let it continue.
AdiOS is completely free and available to download from Veracode's blog. If you have a lot of iOS apps, it may take some time to run, and if you haven't synced your iOS device with your Mac in a while, you may want to do so, just to make sure any apps on your phone are also reflected in iTunes.