[ballenf]

The metadata of our conversations is really more important than the content most of the time. Especially if FB is tracking the conversation participants before and after the chat.

If we chat and then shortly there after you search for some fringe political group, it's pretty safe to see that as a strong indication that I'm involved with that group. Or if my geolocation places me at some political event and we chat during or just after it, you're implicated.

FB doesn't need the contents of messages, they need the metadata plus all the other user tracking.