The content of ads rarely matches with something I'm actually interested but uninformed in. The most wasteful ads are probably the ones about products I already bought, or the ones about products referring to a conversation partner or shared links to websites which hold interest to the sending party, not the receiving one. The ads are very targeted but not targeted at someone who would ever buy the advertised thing.

If only one could 'scan' the product they just bought to no longer see any ads about it...