I have only posted re a personal situation once. I found that because the nature was so personal and involved others, it made me very aware of how I phrased the post. I took extreme care to not make the others concerned out to be the bad guys, and I don't believe they were bad guys at all. It was purely frustration at the time.
I posted to get others views and to make sure that I wasn't overlooking something. It was mainly to see if I was taking everything into consideration and maintaining the best balance for myself as well as the others involved.
Sometimes it's hard to know if the line you have drawn is the right or best one
I don't know if that makes posting about others without their consent ok. I think it is ok if you are careful to stick to just the facts and ensure it is not a rant. My experience was quite funny as the person I was discussing appeared here without my knowledge and gave quite a lengthy rebuttal... it all worked out in the end as it prompted a discussion and cleared quite a bit for the both of us.