Questions about HD Cameras... (noob alert!)

I'm a noob when it comes to video. Let's start with that.

1. Can a HD video camera be used with iChat or Skype (not using the camera to record but to use it to pass the video to one of those programs)?

2. Which media format is better: tape, DVD or hard drive?

3. Can a good camera be purchased for under 1K?

4. Do I need 3 CCD?

Thanks all!