You are right, it can be dangerous to meet people in person that you only know online. People can represent themselves however they want - how do you know he is from your hometown? How do you know how old he really is? How do you know he is really nice in actuality? Think about how easily you could change your whole self while online - your age, what you look like, where you live, what you do for a living - it could be fun, easy, and no one would ever know. However, it gets dangerous when predators do this looking for vulnerable people.
Check out our answers to Sex On The Net and Met Him Off The Message Board for more information. Be skeptical about who you are meeting online (knowing how easy it is to misrepresent yourself) and be safe. Protect your personal information online - especially with people you do not know in your real life.
Two good websites for teens on keeping safe and having fun while on the Internet are Cyberangels.org and National Center for Missing and Exploited Children