I think the problem with a lot of people my age is that they deal with the concept of commitment, and they find that very idea to be frightening. And I think it also destroys a lot of relationships. Whether that be because people are afraid to commit to another person or because they are pressured into committing to one person.
I don't think commitment only scares young people, but people ranging from all different age groups see the idea of commitment as a big and scary idea. But I believe that if it is the right person your fears of committing to them won't be there. I think if you even have the slightest doubt about staying loyal to someone you shouldn't go through with it.
I think it is especially scary for younger people to commit because of their age. They are fearful of choosing to be with someone at such a young age might hinder future relationships or that they might miss out on other "fun" experiences with a multitude of people. And I think if you're not ready or if you think you're too young to make a commitment to someone don't do it. Monogamy isn't for anyone, and lying to yourself won't get you anywhere and it will end up hurting a lot of people.