Videos autoplay for me
At Daily Kos, our policy is that no video or audio content should autoplay. That's the rule for both advertisements and content created by users. Sometimes users inadvertently set a video as autoplay when embedding them. It's appropriate to leave a comment asking the user to turn it off and/or to let us know at helpdesk so we can try to address it.
Our ad network is not supposed to send us autoplay ads, but sometimes they mess up. Let us know the product or advertiser, and we can block them manually. It will help us to know the page or article you're reading when the autoplay ad interrupts. Since ads are so finely targeted now, it might not be possible for us to identify the culprit immediately, so the more information you can provide the better.
However, sometimes there are curious cases where videos autoplay for only a few people. There are some great tips here for debugging it if it is happening to you: