Online video represents only a small piece of the total advertising pie, but the growth in streaming ad revenue is becoming more of a threat to the broadcast medium that supplies most of the high CPM content. Hulu is a case in point, as Mediaweek and paidContent sources point out the ways the site’s ad sales team often undercuts the network media buys for both streaming and broadcast. Sources tell paidContent that some of Hulu’s broadcaster backers, which include NBC Universal, ABC and Fox, are experiencing growing frustration after hearing from media buyers that the video site’s ad sales often offer discounts on ad sales. At this point at least, paidContent is told, the situation is more of an annoyance for networks, than serious damage, since the dollar amounts remain comparatively minuscule.