At best, useless. At worst, detrimental to the experience. It's a good way to drive me away from your site. I can't think of anything I hate more (in design ter

At best, useless. At worst, detrimental to the experience. It's a good way to drive me away from your site. I can't think of anything I hate more (in design terms) than the current trend of auto-playing videos following you down the page.