I think the ads were limited to XDA but Tapatalk claimed there was some kind of "auto opt-in" for forum owners. A bit out of order imo and I've never seen ukb/ukcaving serving ads to Tapatalk so I reckon that's bullshit. Either XDA or Tapatalk were trying it on, paid apps should never had ads of any kind.
Anyway, I only ever saw them on XDA and now they've gone away.