The at the bottom of most (all?) pages is a vertical ‘skyscraper’ banner - it appears at the left of the page with a massive empty white area next to it. Why not just use another horizontal one like the one at the top? - it might even sit alongside the ‘Posting Rules’ box (i.e. people might actually see it).
I have passed your suggestion up to Ed.
The idea was to have one of each standard ad type (vertical, horizontal, squarish) on each page on the site, so we could accommodate whatever ad orders came along. I admit what we have now isn’t beautiful; Jerry just kludged it into the template. If we ever get ambitious, we’ll have to work up something more elegant.