What are the qualitative differences between IM program and a 3d environment?

I think MSN it's easier to learn. I'm thinking about my mother: was not difficult to explain her how to use MSN while I think 3D words are too much for her. What I'm tryng to say is that maybe MSN allows more adult/old people to get involved in the chats. Another big difference is that MSN allows you to socialize but only between your contacts (people you already know), while in 3D worlds chats there are many people that you don't know and you can speak them at any time. I prefer MSN to socialize, even if I really appreciate the opportunity to know other people that 3D words give you. When you meet people in this way you don't know nothing sure about them: you only know what they tell you. When you start to know a person you use all your senses to understand who she is, but in 3d worlds this is not possible, that's the reason why I prefer to communicate with people I've met face to face at least one time in my life