I have one set up, but it is not automatic at the moment. I advertise on numerous webmaster sites but it seems that I still don't get enough traffic for such a program.
I am also going to set up a sponsored link section on the side for each category at a cost per month, and maybe in the future a featured section for a significant one time cost.
These things will boost my revenue, but not my traffic which is what I am focusing on for the time being.
