Well, think of it this way, the limelight is the new cancer and crack cocaine. Once a person gets addicted, they want more and more until they either run out of money (sell out) or die (burn out). And that's when they sink to reality television. I mostly think they're in it for the money, the fame, and/or because mommy and daddy want them to so it'll be good for their own reputation/fortunes.
That last point is the case with some children "stars" that are forced onto some of these talent shows and what not. Now don't get me wrong, there are plenty of talented kids out there that would make wonderful singers/actors/dancers etc. But I can't help but wonder how many of those parents are actually supporting their kid's talent rather than opting for their own fifteen minutes of fame. Hollywood's getting younger, however, it still has yet to get better. If anything, the underpaid artists behind the scenes seem to be better at making a movie than today's actors/actresses do. (Plus they seem to confuse cold, emotionless and monotone with dramatic.)
Well, all in all, I just feel that actors and musicians of today are way overpriced children whom try to add another digit onto their salary count by branching off into other forms of media.
Oh, and if Bieber's on CSI, I will laugh if his character is the victim, but I doubt it will happen.