154 App Empire BANNER ADVERTISING As the number of customers with smart phones increases, more adver- tisers are switching to mobile advertising to reach their target audiences (Figure 9.1). As intermediaries, mobile ad networks handle the sales and placement of mobile ads. Advertisers can buy ad space from the ad networks and developers can use their apps to display the ads. The advertisers benefit from the sales that result from their ads, and you, the developer, earn revenue from the ads. The ad networks keep 40 percent, and the developers receive 60 percent of the proceeds from advertising revenue generated from this process. If you have a smartphone, you probably have seen ads on the top or bottom of your screen inside of an app before. The developers of