I've been trying to find some information on placement targeting. I turned it on and now have two sites targeting something of mine. I just read somewhere that I have to make channels targetable. I did not do that, yet I have two companies signed up to target my sites? Does that mean that their ads won't display until I make that change? And how do I determine what sites/channels the advertisers wished to target? Does placement targeting work like the rest of Adsense where the advertisers bid for placement? The two companies who have targeted me are related to several of my sites and would seem like a good match but at the same time I wonder if their ad is replacing a more expensive one. Seems like placement targeting could be a solution for a site where the Google spider is mis-matching the ads. Has anyone used this feature and how did it convert for you?