Unfortunately it's an age old problem that'll never fully disappear, It seems that the advertisers only join to advertise so they obviously wont be checking out the rules. We Mods do try our best to delete such adverts but can only delete the ones we find, it does however, help when you guys PM one of us to make us aware of such goins on, this means, when there's no Mods around you lot are our eyes and ears so to speak, because if there isn't a Moderator around it's quite easy for said ads to disappear onto to next page on a busy day.
Some times it appears that we just ignor the ads but in reality we're deleing all that we find. In most cases us Mods can see the deleted articles and have a gander, even when they've been deleted to everyone else, this makes it a whole lot easier to manage.
Hope this helped