It's used for acne and folds mainly. Don't think surgeons would use it to build up chin or jaw, unless it's in a third world country or something like that, maybe Brasil, but maybe I'm wrong. You read horror stories about permanent fillers. Fat grafts appearantly dissappear after a couple of weeks, unless it's a special method or something like that, like Kavan posted, but even then I have my doubts.
From what I can see, when people use a bit of filler, it doesn't make alot of difference, but when they use alot, it really makes a difference. Some people inject it themselves. I would be too scared to do that (no madical background, weak hands). The good results from fillers are the only results where I saw the super sharp angles. Even SJ appearantly, according to some users here, had those extremely sharp angles from fillers and not cw.