"What happens to some of these celebrities that eventually drives them over the edge to do more and more outlandish behavior? Do they become so consumed with wanting to be in the spotlight that they have to keep reinventing themselves to stay in the media?"
I think it's like ambition, initially they reach their goal, but they then lose sight of why they wanted what the finally got in the first place. Like Icarus they want to try to push fate a little and get a little more and more. They are never content until God Himself has to step in and push them back and possibly, if they do not stop climbing, take their life.
As for children who pay for their parents' actions, that is quite true. I imagine that Bindi (Steve Irwin's daughter) still misses her Dad, but can't really mourn privately since Mommy Dearest is determined to carry on his legacy. I think it's wrong personally that she's supposedly already doing a show. People should realize that it isn't all about them when they have kids and should always factor in their child's needs when making decisions.