Regardless of whether the ads use JS or not, the page overhead is the offense. The advertisers are using your gear to - theoretically - sell stuff to you. They not only expect the use of your gear for free, but hope you will toss in a tip as well. They could stick to static ads using minimum real estate on the screen, ditch the animations, voice overs and the rest of the television ad wannabe cruft and the number of complaints and contempt directed at the industry would almost vanish. But broadcast TV is dying and the admen want a new home with a minimum learning curve.