Don't believe in the hype, being skinny isn't all that. Like AOX81 said, some can't help it, I eat and eat, yet it is so hard to gain weight. There's a dark side to being thin: a lot of guys only like you just because of it and you're a walking target w/ girls. It can also get your a$$ beat when you're young.
*edited* as I typed that there was a chick on the Early Show with a book titled "Skinny People are Evil"