1. Chat rooms are internet areas where anyone and everyone can "talk" freely about everything and anything.  The dangerous part is that anyone can be anybody they want to be.  You do not know if the 21 year old single female your corresponding with is not really a 45 year old male.  You can't even trust the pictures that are posted.  It's easy to scan or download pictures from anywhere.  Sexual predators love chat rooms.  They pretend to be young children on the internet and then get your child to chat with them.  Eventually a trust relationship is built up.  The pervert will try to get your child to reveal information about themselves and even go as far as try to meet them somewhere "safe".  You should not allow young children to go into chat rooms.   Chat rooms are supposed to be monitored by the company that provides it.  There have been cases where chat room monitors have been fired for engaging in inappropriate behavior with persons in chat rooms. 

2. Instant messaging is a big thing now.  Also with IM (Instant Messaging) you don't know who the other person really is. Sometimes unknown "buddies" get on your child's buddy list and they don't know who the other person really is.  As a parent or guardian, you should know who is on that buddy list of IM.  There are many ways to IM.  There's MSN Messenger, AOL AIM, Yahoo Messenger for example.  There are also Blogs (Biographical Logs) and Vlogs (Video Logs).