Despite the appeal of one agency handling all of a brand's digital duties, an increasingly complex and specialized marketplace requires that marketers tap multiple agencies to execute their interactive strategies. That's according to a new report from Forrester Research, which finds that multiple agencies are key to success because interactive marketers need to outsource certain skill sets, and because agencies help marketers stay ahead of the curve in a fast-changing industry.

"The complexity of the interactive landscape is creating a fragmentation of interactive agencies, which in turn is creating a whole new set of challenges to marketers," said Forrester analyst and the report's author Sean Corcoran. "Interactive marketers should prepare their organization for even more agency partners and educate their procurement teams on the value of these relationships."

According to the report, interactive marketers have a wide range of responsibilities, so it makes sense that they typically rely on their agencies to cover a wide range of services from creative, to Web development, to search marketing and more. Yet, technology has forced the overall agency landscape into flux, and this creates challenges for marketers.

Four out of the five interactive marketers surveyed by Forrester between August and September reported using at least one agency. Agencies have to cover a wide range of responsibilities, and have in fact built specialized skills to help fill the gaps in their capabilities. Yet few agencies, if any, can offer best-in-class services to meet all of their clients' needs, according to Corcoran. "More than half of the marketers we surveyed use at least two agencies for interactive services, and one out of four use three agencies or more," he said. "Yet most interactive marketers would prefer one agency to handle it all."

Interactive marketers need agencies to keep them ahead of the curve, as one of the major roles of an agency is to stay abreast of the emerging trends in the industry and educate its clients.

According to Forrester, agencies are typically in a better position to do this than their clients because the agencies often have dedicated teams working across several clients at once. What's more, many agencies invest heavily in these areas. For example, R/GA has Future Vision, a team dedicated to providing its clients with a perspective of the digital world in the near future to help them prepare their strategy.

Unfortunately, most interactive marketers don't feel they can turn to their traditional agencies for much help. Only a quarter of the interactive marketers Forrester surveyed said they believe traditional brand agencies are equipped to handle digital work.

And while some agencies with traditional roots have grown successful digital capabilities, many still lag behind, leaving interactive agencies with significant opportunity to make inroads in their clients' businesses.

As technology's role in marketing continues to become more important, it also is creating a fragmentation of media consumption and a complex landscape overall, according to Forrester.

While interactive marketers mostly use their agencies for staple services like creative and Web development, the agencies are beginning to adapt and take on new roles outside of their typical walls.

For instance, one out of four interactive marketers Forrester surveyed reported using their interactive agencies for brand strategy, while 26% reported using them for offline creative. To boot, nearly one out of three reported using their interactive agencies for social marketing.

While all are necessary evils, Forrester does concede that more agencies will lead to more administrative work, higher costs, and more reliance on "the often dreaded" procurement team.

Also, while the big agency holding companies such as WPP, Omnicom Group, Publicis, and Interpublic offer their clients a wide selection of agencies, most of the marketers Forrester surveyed aren't taking advantage of the offering when it comes to their traditional brand agencies and interactive agencies.

Only one out of four interactive marketers that Forrester surveyed had primary interactive agencies that were affiliated with their primary traditional agency.

Meanwhile, less than one in four of the interactive marketers surveyed by Forrester believe they were ready to assume full responsibility for a brand's livelihood.

This news story is important. I recommend that everyone read it.