Some major blog ad networks are expanding rapidly, and therefore confronting inevitable growing pains.

Federated Media recently added a new automotive category and some 20 assorted blogs, including Guy Kawasaki's, boosts the blog network's monthly impressions to "hundreds of millions," Federated's chairman, John Battelle, told ClickZ. However, the recent batch of acquisitions could be the last for a while as Federated seeks to build the infrastructure needed to support further growth.

Competitor AdBrite is also growing quickly, having recently added the 20,000th site to its network; the company plans to shortly introduce new demographic planning and campaign management tools. Though the network's roots are in blogs, it has expanded to other publisher sites, and blogs are now only a small part of the network.

Meanwhile, Henry Copeland's BlogAds network is moving to a more robust platform to accommodate even more sites. Copeland wants to expand the stable of blogs available to advertisers, and also increase the number of "mini-networks," blog segmented by topic, such as football or politics. He also wants to arrange ad buys on political blogs by state, in time for the 2008 election.