Okay I think I might have a suspicion as to a potential culprit....
I had another add-on that I downloaded in Firefox, but not in Chrome - a YouTube video downloader: http://addoncrop.com/youtube_video_downloader/
I installed this because AntVideo Downloader doesn't always successfully download Youtube Videos for some reason.
I removed this add on, and went back to the same site that was generating all of those pop-up tabs, and lo and behold, I'm not seeing the new tabs popping up each time I click a link anymore.
I guess it was that add-on that was causing the ads to pop up in new tabs? Does this make sense?