Price for a top banner is more than 3 times the cost of a bottom banner.
The SS banner is at the top, so one could easily scroll down a couple of inches and not have it in view and still see all the boards functions such as PMs and the chatroom.
Now, as mentioned previously, the banner is the way it is because of marketing. It's excellent marketing - after all, ALL of you are noticing it and you know what the company sells.
That being said, I am sure something can be worked out where the banner can get changed or moved, but for SS not to lose exposure.
Maybe like what edge said - all of you can put the link to SS in your signatures and promote it every chance you have. That way, any loss of exposure that will happen from moving the banner from the top will be recovered because of you guys.