The challenge over the next 12 or so months, according to many experts, is for publishers and advertisers to find new ways to maximize the value of their relationships with ad networks. Publishers are eager to end the channel conflict that hurts their own direct sales efforts, while advertisers are starting to see the advantages of finding cost-efficient ways to expand online from direct marketing into branding campaigns, with their entirely different goals and metrics.

For years, ad networks have been built and sold to aggregate publisher inventory and to enhance advertisers' targeting capabilities. But more recently, we've seen the growth of vertical ad networks, which offer advertisers entirely new opportunities to optimize their ROI and better target specific users.

We're also seeing the advent of online video, which could present new and powerful opportunities for brand marketers to colonize and develop online territory.

And the ongoing consolidation of the market -- everyone agrees there won't be room for more than a handful of horizontal ad networks -- should create opportunities through greater scale to optimize retargeting capabilities in ways that vertical networks, which might not be able to track everywhere a person goes online, simply can't match.

"You'll see the bigger publishers start to announce they're working with only two or three ad networks," says Mike Cassidy, CEO of Undertone Networks, an online advertising network. "One of the problems in the marketplace has been too many networks going to the market and offering inventory cheaper than the publisher. Ultimately that hurts what the website is trying to do."