Wouldn't people have to friend them to be able to be seen by them (or at least privacy settings can make it so only friends can see your posts, pictures, etc.)?
I remember the days back when they were advising people not to have lists of brothers and sisters so that when the great tribulation comes, "they" can't find out who all the JWs are. This happened when a friend of mine wrote a little program to help the elder in charge of the ministry school schedule it and create formatted schedules. Everyone got a sheet with their name highlighted when they had parts. This was in the late 70's/early 80's before word processor programs. They didn't like that his software consisted of a database of all the people in the Ministry school because they didn't want that sort of list available to authorities. Never mind the publisher records that I'm sure were also laying around. And which would have been presumably larger than those in the ministry school.
With Facebook, everyone could be linked and much more accessible (assuming the authorities got control of Facebook).