MSN Tuesday began incorporating behavioral targeting features into its paid search program, adCenter. With the new service, advertisers can arrange to have their pay-per-click ads shown to users who MSN has identified as likely purchasers based on their Web-surfing history.

For the program, which the company previewed in February, MSN will scrutinize people's searching history and sites visited to determine their likely interests, and then create 18 audience segments. The segments include mobile users, Internet power users, gamers, movie watchers, new/expecting moms, parents, and several categories encompassing travel searchers, and auto buyers and researchers.

With the new service, for instance, a car company can arrange to display ads to users who are already identified by MSN as "auto buyers" when they use the site's search engine.

The behavioral targeting component of MSN's adCenter ads is one of the bids the company is making to differentiate its search engine marketing product from its dominant competitors, Google's AdWords and Yahoo Search Marketing. MSN has been touting the targeting capabilities of its engine, which includes targeting by daypart, demographic targeting, and geographic targeting, since the product first launched in beta last August.

Ellen Siminoff, CEO of search engine marketing firm Efficient Frontier, said that although the targeting features do offer some degree of differentiation, MSN search still has a ways to go before it is competitive with Google and Yahoo. "I think, at some level, it's good for them to be offering something ahead of others," she said. "But they won't be able to call themselves a leader until they have share closer to what Google and Yahoo have."

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