Over the past few weeks, a debate over the use and growing prominence of ad networks and exchanges has been gathering. The recent shuttering of ESPN’s (NYSE: DIS) and the Washington Post’s (NYSE: WPO) respective ad nets, as well as the news that Forbes was starting another one, have given legs to a comment made at the Interactive Advertising Bureau’s annual conference by Martha Living Stewart Omnimedia’s Wenda Harris Millard (pictured, above, left) warning that media companies were selling web inventory like “pork bellies.” I interviewed a number of execs, including Millard, MSLO’s president of media and new IAB chair, and AOL Platform-A President Lynda Clarizio (pictured, above, right), about their views on the buying and selling of media companies’ online ads, including some at a recent IAB conference with programming inspired by the debate.

All ad networks are not created equal: If all sides can agree on one thing, it’s the need for greater clarity to what’s being sold and where it’s being placed. Until then, the divide will remain. On one side, there are the vertical ad nets run by media companies like CondeNet, MSLO, Nickelodeon’s ParentsConnect Network, CBS’ network of local TV station sites and Forbes’ forthcoming financial network. Verticals promise control over ad sales and placement. On the other side are the sale of remnant ads (ad space that has gone unsold and is typically offered by web publishers, often at a discount) handled by Google/DoubleClick, Microsoft (NSDQ: MSFT), Yahoo (NSDQ: YHOO) and AOL (NYSE: TWX).

Their views here at paidContent.org