I understand all this as I've had similar things to all the above happen to me on occasion. Perhaps this occurs because through a social networking site people hear from us every day who used to not really hear from us any other time than an occasional card, phone call, wedding, funeral, holiday, occasional e-mail, or family reunion. Now those same people hear something from us everyday, so there is a greater chance we will say something they take issue with. One little status blurb that you think the recent health care bill is scarier than any book Stephen King has ever written can unleash a plethora of nasty comments and send your third cousin or your old friend you met years ago at summer camp packing. Delete, delete, delete they go.
I have to confess, I don't mind. I figure first of all, if they are that shallow to get upset over the fact that I posted in my status that I took my daughter to see Twilight or that I shared a swimsuit photo, let them go. Second, if they find out more about me and that leads them to not want to be in relationship, hasn't it served to more help me figure out who is important in my life and who my real friends should be?
Some consider it hurtful...I consider it a helpful, time saving service.