Sorry, Kristin, you're dead wrong
Kristin, if you install the Facebook app on an iPhone, it will read all of your iPhone Contacts and send them to Facebook's servers. PERIOD. There is no setting to disable this; it's done when you install the app, whether you like it or not. This has been documented heavily on the Internet. I called Apple tech support, and after denying it, they admitted that it's true.
Try it yourself: Open Settings on your iPhone. Now pick "Privacy," and "Contacts." You'll see a list of apps and you can choose whether or not they can access your Contacts. See the problem? Facebook isn't listed. That's becasue they take your Contacts without asking. I figured this out for myself when Friend suggestions showed up for people who I'd had only fleeting business relationships with, who don't know any of my friends. If a "Friend" suggestion shows up for someone in your Contacts list, and zero mutual friends are listed, how do you think Facebook got the name? From you, of course.