Ask HN: Popup/overlay videos that you can't close?

I've started seeing these... I'm not sure exactly what the correct term is, but they're small videos in the corner of a web page. They have their own "x" in the top-right corner, and a pause icon in the lower left corner. They're used for ads, and for some actual content as well.

I've started seeing some of these where the "x" and the pause control are a lie. Clicking either one does not do what you expect. Instead, it brings up a new tab. Always (or maybe almost always?) these are ads, rather than ancillary content.

Is anyone else seeing these? Any idea how to actually kill the video subwindow on the tab you're viewing?

(I'm mostly seeing it on Yahoo. Maybe I should just not go there?)