The issue of advertising on the Internet can be problematic. As opposed to advertising on a medium like television or in a newspaper, the market is far more fragmented, with significantly more potential channels available to reach consumers. While search engines, the gatekeepers to the internet, provide a good way to reach a consolidated population of consumers, advertisers looking to advertise on specific websites will have more difficulty reaching lots of people. Which is where advertising networks have stepped in.Advertising networks, such as undertone networks (www.undertone.com) will buy ad space on a large number of websites, and tie all of that ad-space into a network. These networks then offer access to their services — any number of advertising strategies implemented across the entirety of the networks adspace, at varying rates — to interested advertisers.A good example of an ad network is the one detailed in this article: http://money.cnn.com/2008/06/16/technology/music_blogs.fortune/index.htm. Music blogs were having trouble attracting advertisers because they didn’t have a large enough following to make such advertising investments worthwhile. Likewise, advertisers would have liked to reach the demographic represented by these music blogs — tastemakers — but found the market was too fragmented to make advertising there a viable option.An ad network solves both of these problems:For the blogs there is a network effect present. There’s incentive to join such a network that increases the greater the number of other such blogs sign up to be a part of the network, because the more blogs are a part of the network, and the more consumers reachable through the network, the more advertisers will be willing to use the network.Such networks have become more and more common as a way for advertisers to reach consumers on the Internet, and networks such as the music blog network (called vertical networks), which aim to target a particular set of consumer interests, are a great way for an advertiser to reach a consolidated base of potential customers.