It has nothing to do with there being other sponsors already. Some of my adwords show up as sponsored, right below the sponsored ads. It has to do with MONEY. Google has some type of algorithm for figuring if you get into the sponsored listings or not. In general, when I raise my bids above .30 cents, most of the time I will move into the sponsored area. However, I'm pretty sure they also take your CTR% into account also. I have a few keywords that just won't go into the sponsored area no matter how high I bid. I have never been able to fully figure out the exact criteria for getting into this sponsored listing area.