It never ceases to amaze me really.
About a month ago a friend of mine joined a group on facebook relating to a medical condition she hadn't told any of her friends she has. She is a very private person, so I wouldn't have expected her to tell her friends about her medical history. but by joining this group she has inadvertently advertised the fact to everyone on her friend list.
And today I have noticed that another friend has joined a group, again relating to a medical condition, but this time wrt her unborn baby.
And on a lighter note, another friend posted on his status that he was going to take a sicky from work that day, am certain there are people who work with him on his friend list.
I just think that people forget who is looking when they (I think often unwittingly) expose their lives to the people they wouldn't expose them to in rl.