The address book in smartphones — where some of the user’s most personal data is carried — is free for app developers to take at will, often without the phone owner’s knowledge.
Companies that make many of the most popular smartphone apps for Apple and Android devices — Twitter, Foursquare and Instagram among them — routinely gather the information in personal address books on the phone and in some cases store it on their own computers. New York Times
I was painfully made aware of this invasion of my privacy many months ago, so I went in and deleted my address book that Facebook had taken without my knowledge.
After I read the above article, I went back to Facebook to check and make sure they didn't import them back in after I deleted them the first time. To my amazement, my Facebook phone app reimported them, probably after one of the many Facebook "updates" to my iphone.
Finding out whether Facebook has your address book is no simple task! They make it very difficult for the average user to locate this information. If you want to know if Facebook has your address book/contact information, feel free to click on this link to see if you're an unwilling participant.
Remember that every time you update your Facebook app on your iphone or Android you will probably have to go back and manually remove it. Sneaky sonsabitches!