Why Full Screen Video is SO SLOW?

It is not a daylight discussion, but It is not the first time I got myself researching about that with no success at all.
After all, what could be done when Full Screen Flash Video consumes up all the computer resources?

  1. Is it a hardware/driver issue?
  2. Is it about developing best-practices?
  3. Is it some especific configuration on FLV exporters?
  4. Is it a Flash Player limitation?

I have noticed some sites provide a really smooth full-screen video experience, but some others shows themselves up with a hell of video performance. My inclination, in a first approach, is towards thread 2. I have done some tests and all of them ended up in a clunky horrible show-time.

Anyone here has some tips to share?