1.1. Can't always access them, as the server may be down
1.2. If you want to talk to a certain person, and they're not online but you keep the window open to wait, other people can message you and so annoy you.
1.3. You can often keep up with the news without going on news websites.
2. Social Networking
2.1. Facebook
2.2. Twitter
2.3. Blogging
2.4. Wikis
2.5. Forum
3. Voice Over IP (VOIP)
3.1. Some people prefer voice communication
3.2. Immediate reactions to comments and questions
3.3. Other person needs to be avaiable at the time of the conference