HTML5 Video is just an example of shitty browser behavior, as for some reason, every web browser maker seems to think that autoplay videos are great. They're not because sites are abusing it.
Worst, some sites these days will waiting until you've scrolled down a bit before they start playing a video, leaving the user to locate it and stop it.
As for Flash, it was indeed bad, but at least I had the option of not installing it.
> every web browser maker seems to think that autoplay videos are great
Huh? This has nothing to do with browsers; it's purely a site author decision. Autoplaying videos is a site author decision -- and one that they already frequently made before HTML5 video was widely available.
Not really. Browsers just need to default stop autoplaying videos out of the screen view. Or better yet what they did to popup blockers. Give one chance to behave well, if the site doesn't then it gets blocked and the user has a notification that autoplay was disabled.
Blocking scripted calls to "element.play()" really sucks for Web developers building games and other kinds of apps. Safari on iOS did this and it was horrible for developers.
Firefox and Chrome let you mute tabs. Firefox Nightly also blocks playback in any tab you haven't actually looked at yet. Other than that there's not much they can do.
Worst, some sites these days will waiting until you've scrolled down a bit before they start playing a video, leaving the user to locate it and stop it.
As for Flash, it was indeed bad, but at least I had the option of not installing it.