I really liked Guyon's idea about the paddles so I implemented the game using mouse control, only for 2 players at the moment.
You can get the server and client here:http://www.box.net/shared/5703uihspa
1. You can swing the paddle really fast and go through the ball. For simplicity sake I have not addressed this. For now, you have to resist the temptation to swing at the ball.
If you know of an easy way to do this that won't add too much complexity to the soon to be tutorial
then please let me know and I'll incorporate it.
2. Over internet. My guess is there will be lots of lag with players moving their mouse so quick. I plan on releasing the tutorial then looking at another library (plus interpolation/prediction) to handle online lag.