Billboards run all over the site now instead of just the forums, so they reach far more players and the impressions you buy get spent quicker. Every purchase tier now grants ten times as many impressions for the same Cash Shop Credits, so a single buy keeps your banner running much longer.
I really am excited to see them at other places around the site. I really do click on them and check out what they want me too and now I'll be able to do that more! I expecially love the silly ones xD