I hear you OP, sometimes when a FB friend airs out their personal relationship issues over FB I both cringe and feel sorry for them. My thinking is that perhaps they don't have anyone in real life to talk to about it, are lonely and want someone to listen and validate what they are going through.

I use FB for memes mostly, and to keep up with certain groups I'm in. Some people use it as a support place, possibly because they have no other support system. When I think about it from this perspective it makes it a little more understandable.