The problem is that HTML 5 video is really useful for replacing animated image formats. The technology in modern video codecs is way superior than gifs, etc., and the real impact of that is
greatly reduced space/bandwidth consumption, like
orders of magnitude better.
Just as we start to leave gif in the dust, Facebook pulls the dick move of auto-enabling sound on all auto-played HTML 5 content.
I think that Google's solution of refusing to autoplay videos with soundtracks is a good compromise which will allow us to continue to enjoy the benefits of modern video codecs while simultaneously preventing built-in video support from gaining the bad rap that got attached to Flash.
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EDIT: Reply to rhizome, since I'm not allowed to post for a while for having an illegal opinion on Kubernetes.
I'm not suggesting that the technology would be eliminated in its entirety, but disabling autoplay of all HTML 5 video neuters its use as a replacement for animated gifs.