Impressions may be through the roof, but social networks aren't the apple of a serious media buyer's eye anymore. Get the inside scoop on what's working in that finicky space and why some brands just won't go there -- period.

Social media, with its growing army of devotees and shockingly low clickthrough rates, has long been a riddle for media buyers. Sites like MySpace and Facebook should be a natural fit for any buyer looking to achieve reach and frequency. In turn, that opportunity should result in an influx of major brand advertisers. But so far, brands have been reluctant to use social networks, at least when it comes to buying banner ads.

"Banners have long been the province of major brand advertisers, but we see that a lot of media buyers are carving out social networks right from the get-go," says Mark Kahn, CEO of Traffiq, an ad exchange that matches buyers with sellers.

According to Kahn, 25 percent of media buyers nix social networks before the first piece of their campaign is put in place. Another 25 percent of media buyers turn to social networks only when they realize their budgets may not be enough to achieve the reach they had hoped for.

That thinking may help explain two stories this week that tackled the issue of poorly performing ads on social networks.

In a non-scientific poll, Mashable, a blog that covers social networks, found that Facebook appears to lead the pack when it comes to serving relevant, quality ads to its users. While that's good news for Facebook, it's also troubling for the sector as a whole when one considers that the most common response given was that ads on social networks are "all equally horrible."

If Mashable's insights feel true, recent data from Pali Research suggests that where there's smoke, there's fire. Richard Greenfield, an analyst for Pali, issued a report criticizing Google for regularly serving irrelevant ads on MySpace. According to Greenfield, searches for proper names -- a common query for MySpace users looking for their friends -- often yield products such as DNA testing kits. While Greenfield had no solution, he did suggest that Google needed to refine its algorithm for social networking.

But a better algorithm may not be enough to save banner ads, and the truth is that some advertisers are having success on social networks, provided they steer clear of the banner, according to Joseph Dumont, a partner at the Questus advertising agency.

While Questus works with brands in social networks, banners aren't high on Dumont's list because they often fail the user test.

"For advertisers to be successful, we need to listen to our actual consumers," Dumont says. "They are telling us banner ads are not working, and that if relevancy can be achieved, they will partake."

That's a big "if," but it's a hurdle some brands believe they can overcome by leveraging what social networks do well, namely targeting people rather than pages.

The social network ghetto?
For Vitrue, a new-style social media marketing agency, the lure of sites like Facebook should be their ability to help brands connect directly with users.

"Social media marketing is a lot like where banner ads were in the late '90s," says Vitrue CEO Reggie Bradford. "We're definitely in the second inning of a nine-inning ball game, and right now not all the pieces are well understood by media buyers."

While media buyers may not fully understand how social media fits into their overall campaigns, sites like Facebook and MySpace are fast becoming advertising ghettos. On the periphery, banners for lower-tier advertisers tout dating sites and pills. For those advertisers, social networks are nothing more than a cost-effective reach play. But at the center of the equation -- where the user resides and company's like Vitrue make their money -- advertisers are realizing that there is a tremendous opportunity for experiences that engage users with brands.

Late last month, Visa handed Facebook $2 million, not for banner ads to run on the site's ever-expanding inventory of pages, but to present a value proposition to users who downloaded the brand's widget. That means the premium inventory on social networks isn't a highly trafficked page, it's an individual user, which is why this week Facebook clamped down on some widget makers who had failed to meet its privacy standards.

So are banners really dead?
Although banners on social media sites may be the preferred ad unit for advertisers facing budgetary constraints, evidence also emerged this week that the banner may not be as hopeless as some have suggested.

While MySpace and Facebook battle it out for the lead in the social network race, the true challenge may come from the rise of vertical social networks. This week, Orbitz, Expedia and American Express Business Travel all made the news in an effort to develop vertical social networks around travelers.

Unlike their horizontal counterparts, vertical networks aren't likely to be so cruel to banners, according to Kahn, who suggests that brand advertisers may need to approach those networks as they would traditional publishers.

"[Vertical social networks] give you the right audience at the right time for the right advertiser," Kahn explains.

If Kahn is right and we are in the second inning for social networks, the middle innings are likely to be characterized by the rise of the verticals. That could be music to the ears of media buyers who have already become accustomed to the delivery of a narrow message to a highly targeted audience.

Michael Estrin is associate editor at iMediaConnection.