I wouldnt do it myself, I barely post anything on there at the best of times so I certainly wouldnt post the details of my latest row with H or whatever!
But I have no issue with those that do, as it makes for very entertaining reading! My cousin was outed as a cheat by his GF a few years back on FB, which I thought he deserved and he took it quite well considering! And my BIL is currently playing out his marriage break up on there with his "STBX" posting long rambling passive aggressive replies to his long rambling passive aggressive messages! Think lots of "It hurts so much when you think that you know someone and then you find out that you dont know them at all....." type stuff. They are both drama llamas and always have been so this latest "breakup" will probably go the same as all the others and they will be all over each other again in a month or so 
But in the meantime, I am hooked! I have been on FB more in the last 2 days than in the previous 6 months :o