[Too]

There is always <iframe>. You can easily embed a youtube or vimeo video even if your core product is not displaying videos. I always felt that iframe is a bit of lost potential, what it needs is a javascript api so that you can communicate back and forth with the frame/plugin, last time I checked this was not allowed due to same origin policy.

After the communication channel is in place it needs a few standard interfaces, maybe there could be some video player interface with play/pause/seek functions. These dont have to be included in any w3 standard, its more of a de facto standard or agreement that if you make a video player and don't implement the IAwesomeVideoplayerInterface, websites will not allow embedding of your product.

What's sad is that it seems like vendors are trying to move away from this model, Facebook is the prime example of this with hosting of a copy of embedded videos and displaying linked news inline in their own format.