They actually make a point of saying that you do not have exclusive rights to a listing.

Where exactly do they say that? They do say that you have intelectual property rights over any text or photos created by yourself which may not be copied by others without your permission but I can find nothing that says they cannot put anything else they want on the same page your listing is on.

They in fact informed all members that they would be starting to put advertisements on the same page as listings before they did it so as with any other update to their terms and conditions that would supercede anything said earlier that specified they would not.