I've only seen a couple of video ads, but they were very annoying. I was reading, when suddenly it scrolled up to the top for the ad (I use Chrome). I scrolled back down and .. zip! I was back at the top again looking at the blasted ad again. It's beyond annoying, but luckily the videos have been a rarity for me.
Even worse, when I had only 15 gigs of Internet a month with Dish Internet, videos ate into that fast. So ads that automatically play on any site infuriated me. I often have my sound off and there were times on other sites that videos were playing in the background and I didn't even know it. I now have unlimited data, but I know not everyone else does. I don't mind video ads, but if they automatically launch, then that's a HUGE pet peeve of mine.
Stepping off my soapbox now.
There are two types of people in this world: Those who can extrapolate from incomplete data.