For a start, I truly believe there isn't a person alive who isn't insecure. No matter what someone else thinks, we are our worst critics and will ALWAYS find flaws. Some of us are just more confident than others about it.
As for beautiful women, there's always the pressure to STAY beautiful; with homely girls who don't change, people don't say much, but when a beautiful girl starts losing her looks for whatever reason along comes the 'What happened to her, she used to be so pretty' comments.
And not everyone thinks Angelina Jolie is beautiful; I look at her and think 'Wow, stunning' but I know other people who don't ; so no matter what you look like, there will ALWAYS be someone who thinks thats beautiful and someone who doesn't.