If you're doing any sort of Internet startup, you should really try to develop an understanding of the online ad market, either to monetize your app or market it.
Ad networks are very simple- they connect advertisers with publishers and take a cut(usually 30-50%) of the advertiser's spend.
The reason BlueLithium was(and remains) so successful is that instead of targeting the entire network of publishers or simply segmenting them by channels/topics, they pioneered some rudimentary behavioral targeting to show ads to people who were more likely to click on them. This led to lower CPA/CPC for advertisers, which means they were willing to pay more for impressions. That led to BlueLithium being able to pay publishers more, resulting in rapid growth for the network.