Technology is another key differentiator.

Representation firms
There is typically no technology involved. The rep firm will represent and sell the site’s inventory. Rather than using technology, their focus is customer service and attention to detail in executing typically more complex programs. They work on behalf of the publisher to meet each advertiser’s goals but do not have proprietary technology that is amortized across all the sites they represent. And usually an advertiser only buys one to three sites from any one rep firm (versus running on all sites, as all sites are not necessarily applicable).

Ad networks
Most of the ad networks, pure or hybrid, will almost always use some sort of technology to optimize advertisers’ campaigns to the site, placements and creative level based on the back-end metrics. Usually there will be a tracking pixel on the advertiser's site for that specific ad network, and the network will then be able to see performance through to the back end (only for their sites) and work with the client to optimize the campaign. The network will employ any number of optimization and targeting techniques with its technology. Be sure to work with the network to determine the best ways to reach your desired audience and back-end goals.