Brad Geddes writes a piece regarding Google launching site-targeted advertising on a CPC basis. Google launched the same thing on a CPM basis sometime in 2005, and I tried it just briefly for a side project, but stopped shortly after because it didn’t bring any conversions. Hopefully the CPC model will change that – it looks like it’s in beta right now, so we’ll all see soon enough.
More of an FYI, but if you’re unfamiliar with Brad Geddes, he’s a well-known PPC analyst and speaker. Google’s even bringing him to Minneapolis March 29th for an AdWords seminar (not sure if it’s full yet or not).