These Google Thingies
In the Vince Gallo topic, we have "Cocaine Users" and "Marijuana Users". Similar links in the Kevin Smith topic. But... if you look back at Travis' British politics topic, the links are very helpful (Liberal Democrats, Labour, Conservative Party, Kilroy). Same for the Lynn, MA topic (North Shore).
So it's picking up on keywords associated with forum content. Interestingly, the more personal topics don't have any topic-specific links at all, so the ads appear to be linked to popular culture rather than a more global seach engine. For example, a larger keyword cache would have put links to psychics & horoscopes for Miriam's "wookin' pa nub" topic. Right?
OK, now I'm even boring myself.