How do you prefer to place banners in the footer (if you do) do you widgetize your footer or prefer just to code the banner straight into the footer.
I always code banners straight in... although I bet just as many people would prefer it widgetized so they could manage it through the WP admin.
i used to code them straight in, however if you create a text widget and widgetise your footer it makes it easier to update the banner code as and when you need to.
I'd just place the code into the footer, it's pretty straight forward and quick. Using a plugin requires finding one, downloading it and installing it (that takes too much time).