Future advertising

Makes sense, ads could be more relevant and valuable if they were matched with entries and articles instead of pages but how to do it or, as important, how to display them? Taking the weblog example, it would be fine for individual archive pages but how about within the main page? You cant really start having little ads (even text ads) next to each posts can you? I dont have an answer so far so I’m looking forward to discovering how this comes about.