The Wall Street Journal's Emily Steel puts it this way: "There used to be a clear division between media outlets... which sold ad time or space and ad agencies, which designed and placed the ads on behalf of marketers. One reason [for the division]: the potential for conflicts of interest if an ad agency owned by a media company was seen to be unfairly directing ads to its sibling media outfits." But times are changing. Steel goes on to cite other examples of the new pubvertisers, including Conde Nast and Wenner Media, both of which have created in-house ad divisions; Gannett Media, which now owns interactive shop PointRoll; and Google, which has "expanded aggressively into ad sales."

I think it's Steel's last example--Google, or, more broadly, the whole world of search--that's the key catalyst in the pubvertising trend. That's because search has placed a whole new level of analytics and transparency into the publishing world; and it's this analytics-based transparency that makes pubvertising possible.

Why? Because advertisers would mistrust pubvertising in environments in which there's little recourse for evaluating the agency's suggestions. It's only when good analytics can show advertisers when they're being lied to, when they're being led astray--and when they're being offered sound advice--that makes it safe to take advice from a source that may have a conflicting interest. Analytics create transparency, which creates trust, which is the crucial element for pubvertising to get off the ground.

And it's the search engines that are leading the way in both providing and leveraging this kind of transparency. From free keyword tools to human sales reps, search engines are kings in advising advertisers how to manage keyword spend. But while they're pushing keywords, the engines also provide clear data on how those keywords actually perform. That transparency makes customers feel secure both listening to the engines' advice on buying keywords, while purchasing those keywords directly from the engines themselves.

Of course, it's obviously in publishers' interest to have ad agencies in-house, because having an in-house ad agency places advertisers within immediate reach. Publishers know this, which is why pubvertising is a trend that will only grow. And to allow that trend to grow, publishers of all kinds will look to offer better analytics and transparency to make that pubvertising possible. I'm not just talking about the MSNs, Yahoos, and Googles of the world entering into an arms race to create better targeting and analytics. I'm talking about even the lowest-tech of ad formats getting into the game, as was the case when print classifieds joined forces with Google late last year.

This has serious ramifications for the future of the ad agency. As publishers look to beef up their analytics and transparency so they can get into advertising, ad agencies will have to beef up their analytics capabilities to get closer to the publishers they'll need to work with--or be purchased by--to survive. That's exactly what happened in the world of search, in which a transparent, analytics-heavy publisher model (the engine) gave rise to a new kind of transparent, analytics-heavy ad agency (the SEM firm).

And so as pubvertising shifts from yesterday's impossibility to tomorrow's new standard, look to a huge surge in the analytics-based publisher, the analytics-based ad firm, and clients who expect analytics-based transparency from both. Meanwhile, Madison Avenue firms who can't keep up--because they can't get up to speed with their data--will face a real uphill battle in the new ad world that looks more like the search world every day.