A few years ago, it was relatively easy to separate online search and display ads from a publisher, marketer, agency and consumer perspective. To publishers, search ads were those that appeared on the results pages of user-initiated keyword queries on their sites (typically via syndication). To marketers and agencies, search ads were those that could be purchased through search engines like Google and Yahoo and appear across their distribution networks. To consumers, search ads were those listings at the top or on the right of search results pages (and, even though many consumers still don't know the difference between paid and organic listings, they sure never confuse them with banner ads).

Then Yahoo Content Match and Google Ad Sense changed everything. Suddenly publishers (large and small) could display "search" listings on their sites without user-initiated query functionality. Marketers and agencies could capture more traffic from their "keyword" buys. And consumers began to see subtle, relevant text ads on content pages of the sites they visited every day in place of "Punch the Monkey" banners.

So how should these keyword-contextual ads be classified? Should budget spent on those placements fall under the search slice of the pie? Sure, they're purchased through search providers on an auction basis, but they are not based on user-initiated queries and, hence, are often no more relevant than a behaviorally or demographically placed ad. And they appear on publisher sites in standard banner, leaderboard, and skyscraper ad units--sometimes even in graphical format with CPM pricing.

And if keyword-contextual ads didn't blur the line enough, consider what MSN AdCenter brings to the table with the ability to target display ads to consumers based on their past search keyword queries. When a person who searches for "home improvement" on MSN and two days later is found on MSN Real Estate and served an ad for Lowe's--is that a search ad? Or, if it's in a banner format, does that make it display?

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