"This mistake is widespread, particularly among name brand companies trying to get their app into the hands of a large customer base. Marketers are too often relying on the traditional marketing activities they already know in an attempt to drive app downloads: online activities like banner advertising and PPC campaigns that target desktop web, offline activities such as TV and radio advertising, and even print marketing.
There are two reasons this approach isn’t particularly effective. First, these vehicles target large mass audiences, many of whom have no interest in downloading and using your app. Many people in these mass audiences may not even have the iPhone, iPad or Android device required to use the app! As a result, user acquisition cost through traditional marketing outlets is much higher than it would be through mobile-specific advertising.
Secondly, TV ads, banner ads or print marketing rarely offer an effective method to click through and download an app, as it requires work. Even if a potential user has a required mobile device on hand, it has been proven that the conversion rates are extremely low in comparison to in-app advertising through mobile devices."