YouTube blows away the competition as far as views, stability, and API. For websites that stream video, it's crazy not to embed from YouTube. Re: Rule 6

YouTube Advantages

  1. Stability. YouTube works everywhere on any device.
  2. Usability. Users get familiar player controls.
  3. Simplicity. Easy to implement via copy and paste.
  4. Traffic. Link your site from the video description.
  5. Search. Google indexes YouTube and people search YouTube.
  6. Sharing. Users can easily linkup or re-embed the video.
  7. Interaction. Comments. Favorites. Likes. Playlists.
  8. Bandwidth. No server strain. Bandwidth defers to YouTube.
  9. Maintainability. Minimal code maintenance.
  10. Network effect compounds the advantages.

Much above also applies to Vimeo. Debating YouTube vs. Vimeo? Don't decide. Choose both.