I usually have several dozen pages open at a time, in five or six windows. My machine just rebooted, and when I opened Chrome again, I started hearing some stupid news show, with advertisements, playing through the speakers. Of course, it was a tech page that I'd opened days ago and immediately turned off the stupid video program in the sidebar; but when Chrome restarted, so did the video. Took me ten minutes to track down the sound, though -- I don't know of any easy way to ask the question "which browser window is making that racket?"
Bloody annoying. I don't at all mind A/V on the web, but starting without a click is *not* cool...