The banner ads I see are all specific to recent searches and web sites I have visited --likely from local cookies.
Those topics you refer to must be things YOU have recently visited.
And, not only are advertisements targeted at you based on where you live and your online viewing habits -- but some online venders even adjust their prices based on those things.
From the security vender AVG:
http://lifehacker.com/5973689/how-we...ium=socialflow