You have to be very careful what you put in your profile (as little as possible), how you set the security settings and who you accept as your "friends". IMO providing you are careful then you can use Facebook as an onlooker. You do not have to post or comment. This forum, and especially Speaker's Corner, can reveal as much as Facebook at times.
Sony Xperia Z5 review: Hands-on with the phone which the Z3+ should have been