I ran a Google search, and I found that the culprit was Adtoll.
Google does not, and has never distributed pop-up ads (but Adtoll does occasionally distribute popup ads). In addition, some of the Adtoll banner ads I saw on Basenotes prior to the spyware fiasco were for some rather rogue websites. So you can display Google ads with confidence... but you should stay away from Adtoll with a ten-meter poll.
P.S.: I use a Mac, and I was not on Basenotes during the spyware timeframe, so I was not affected.