There's an ad that came up today (Osphena?) that prevents scrolling while it plays a video. Whether I scroll up or down, it snaps the browser back to put that video in view. I couldn't read the thread where the ad was displayed.
I had the same problem yesterday on a computer at the gym.
Joining the booster club certainly would solve it, but I still think we should get rid of ads like that if we can, not least because it's a completely obnoxious advertising gimmick.