Brand advertising *is* important, and does deserve some value. Will be interesting to see how this plays out. Clearly, if I am an advertiser and believe in brand advertising, AdSense images make a lot of sense, because (for now) I am getting a lot of free brand advertising. On the other hand, at some point either Google will begin to charge a fee for placement, and/or only image ads which are clicked on will run on the system. John Battelle's Searchblog: What's the Value of Brand Advertising?
Quick! Everyone start flooding Google with image ads!