nothing stops it EXCEPT clicking the on.aol button.....well, it doesn't stop it, it pauses while buffering AND opens a page to on.aol.com. I like Boing Boing too much to speculate about this. However: Not happy about this.
For those with Chrome who want to change all* their plug-ins from "run automatically", you can go into settings | show advanced settings | privacy | content settings | plug-ins, and enable "Click to Play".
That will prevent it from auto-playing when you load the page containing the video. The video is grayed out and you have to 'click to run adobe flash player', but once you do you can't stop it. grrr
*(Please notice this affects ALL your plug-ins, so you may not want to do it).