One of the features many ad networks love to promote is the ability to target by channel or vertical-- such as auto or finance.

But let’s be realistic about the targeting capacity of an ad network and the quality of the inventory available. Much of the inventory available in the network is there because it couldn’t be sold in any other way. Even if the ad network positions itself as a repping firm rather than a remnant inventory aggregator, ask yourself how many huge, scalable branded sites need a repping firm these days? While the ad networks tout themselves as high-quality online destinations, the reality is that much of the inventory is remnant traffic.

Marketers need to be careful about paying a premium for content targeting on ad networks. The real question is whether a network can drive the same value from aggregating related sites in a channel as opposed to a single, scaled site with a great brand in that vertical, such as Yahoo Music or MSN Games. Simply put, most networks cannot do the heavy lifting of brand building.