Because Facebook could figure out WHO YOU ARE TALKING WITH. If you're talking with someone "sensitive", Facebook will know. Perhaps FB needs to use heuristics

Because Facebook could figure out WHO YOU ARE TALKING WITH. If you're talking with someone "sensitive", Facebook will know. Perhaps FB needs to use heuristics to join Caller A with Caller B based upon timestamps, etc. But ZOOM is a messaging app and the IMPLICATION is that FB will know some EXTRA DETAIL about my private life: the other people in it. It's not like this is CANDY CRUSH - duh that's just some game. This is ZOOM, a face-to-face communications app. Much more serious. Apple should flag this for its users on the App Store.