I sometimes get flack for not allowing my DD to be posted by others on FB. I keep her offline. However, I have seen that in recent years I am not alone. My great-niece's mom has rethought having her child online and my sister also keeps her son offline as well. When DD is old enough to post her own pictures, that will be her choice.
I think that the mom blogger who posted something old should have either said she OKd it with the child or not posted it at all. Her child stated her wishes for HER privacy. There has to be other parental material the mother could use. Even though I only have one child, if she said she didn't want to be on my blog, I'd have to rethink my blog if it was about her. She should have a voice.
I also think that we as a society have this "anyone is fair game" mentality. If you are in public, you might be on someone's wall, in their blog, etc. We go to a very large event in the summer and it never fails that rather than send me photographs of my family, people will post them publicly to FB and then tag me. Um, how about asking first? People do not respect other's privacy.
I also think that reality TV is terribly exploitative, especially for children, and we need to be mindful about where we put our kids. If kids who are celebrities in their own right have a tough time, what's happening to regular kids who just can't escape the episode of Wife Swap their parents put them on? Children are at our mercy, right or wrong. We need to protect them.
ETA: Like someone else said, even the funny things DD does that I do mention on FB are carefully chosen. I try to not post embarrassing things about family that would mortify them if they got back to them. If I wouldn't joke about it to their face, I don't post it behind their backs.