Personally, I ignore the sponsored listings. It's weird, but as a buyer, my reasoning is "Well, if someone has to pay to advertise it to me, then maybe there's a reason that no one is buying that product?" The kicker is that as a seller, I completely see their value and want to do it! Yet every time I click the link to start a sponsored ad, my buyer-half holds me back.
Plus, like Julia said, I haven't heard of it doing anyone any real good in terms of sales.