Building on what Shorty's said, I think it's pretty normal for most child celebrities. Not only is your entire life public, but the phases of your life that are the most awkward and difficult (puberty and adolescence) are usually broadcast for everyone to see. They go through a certain way of life most people will never fully get to understand.
And in the end, they're still people. They're human. And they're autonomous beings that can make their own decisions. In the end whatever Miley Cyrus or any of these people do really only hurts their career. It doesn't affect anyone but them. Maybe in the short term (like an unreliable actor might hold up production time with a film because of his addictions), but in the long run people won't work with them anymore.