Andy Beal over at Search Engine Lowdown notes that Google is rumored to be looking for a relationship with an advertising agency.

While Andy, Michael Bazeley and others rightly see this as a (potential) change in Google's marketing strategy (i.e., adding advertising to the mix vs. relying entirely on PR and word-of-mouth), I think there's (potentially) a bigger picture story here.

To date, Google has primarily been seen as a competitor to Overture in the search-related advertising space (e.g., SEM, Contextual, Local, et al). However, with the Yahoo! acquisition of Overture, Yahoo! now has the opportunity to market additional advertising services (across all of Yahoo!'s properties) to Overture's base of 100K+ advertisers.

Google doesn't have a comparable offering... but a strategic partnership with (or acquisition of) a respected advertising agency would give them the ability to co/cross-sell advertising services, influence spend allocation in a multi-channel marketing strategy, etc.

Just as Overture and Google work hard to grow their $20/mth self-serve advertisers into $25k/mth "super diamond" accounts, the ability to provide a one-stop shop for advertising services is too tempting for either company to ignore indefinitely. Remember, in as much as both of these companies are focused on end-user lock-in through services like Google Desktop Search, both must also think about advertiser lock-in through differentiated advertiser service offerings.