Think you've got all the metrics you need? Think again. Experts explain why the web has only just begun to scratch the surface for reporting.

There's a lot of data out there, but the sheer quantity of what's available doesn't guarantee that marketers are looking at the right information or drawing the correct conclusions from the intelligence that has become commonplace online.

For Jonathan Adams, SVP of global media at Digitas, the question of reliable, meaningful metrics is one that isn't addressed enough. So, to bring the topic to the fore, he asked his panel at the iMedia Agency Summit in Austin, Tex., to tell him whether marketers are getting good metrics.

According to Adam Gerber, CMO of Quantcast, many interactive professionals foolishly believe that online is more accountable in terms of metrics than are traditional mediums like print and television.

"The notion that traditional is not accountable is totally [untrue]," Gerber said. "It's the internet that is not accountable because we plan to buy an audience, but we don't really know what audience we're buying."

For George Ivie, CEO of the Media Rating Council, accountability online has been something of a moving target, made more complicated by a disconnect between panel measurements conducted by comScore and Nielsen and the metrics delivered on campaigns from ad servers like Atlas and DoubleClick.

"When we first started working online, we asked what everyone wanted to measure, and the answer was pretty uniform -- measure the ads," Ivie said. "But soon after we started measuring the ads, we also started working on tracking down audiences and certifying panels. What we're seeing everyday online is that metrics are always a moving target."

As for the disconnect between the panels and the ad servers, Young-Bean Song, VP of analytics at Atlas, said the data presented by both sides is only as useful as the marketers make it.

"Yes, there is a disconnect. But it's hard to argue that there's one metric that will answer everything you ask," Song said. "So when it comes down to the metrics that people are using, they are using panel-based data for the planning and buying process and a different set of data for the campaign."

According to David Smith, CEO of Mediasmith, Inc., that disconnect leaves advertisers in a quandary because the goals established on the front end from panel data can't be tracked at the end of the campaign from information provided by ad severs. The result is an apples-to-oranges comparison that makes for a solution that is something of a work in progress. However, Smith a longtime veteran of digital marketing, stressed that web metrics will get better as the industry becomes more comfortable with the abundance of data touchpoints available.

But today's model -- the panel/ad serving combination -- may not be a realistic assessment of the true picture, according to Song, who said there's simply too much reliance on the last click.

"Since the beginning we've seen a drop in the clickthroughs on ads," Song said. "But at the same time we've been getting better at serving more ads to the right people, which is a real paradox. I think what we need to do -- especially as the web becomes a place for branding -- is move up the stream and discount the importance of that last click." 

That statement prompted a discussion on the merits of engagement as a metric. While some say engagement is truly a subjective assessment of the ad's creative punch, others insist that marketers can determine how effectively their message is communicated.

But for Song, the problem with measuring engagement is that it's seen as an all or nothing proposition because marketers want to believe that a user is either engaged with an ad or not. According to Song, reality is a lot more complicated than a simple yes or no.

Smith, on the other hand, questioned whether the industry even has a good working definition for engagement.

But Gerber, who called engagement a "red herring," said it's really a qualitative issue between agencies and their clients.

"When we use engagement as a proxy for the value of a publisher, we make a big mistake," Gerber said.

Michael Estrin is associate editor at iMediaConnection.