  Ads are an important revenue source for mobile app development, especially
for free apps, whose expense can be compensated by ad revenue. The ad benefits
also carry with costs. For example, too many ads can interfere the user
experience, leading to less user retention and reduced earnings ultimately. In
the paper, we aim at understanding the ad costs from users perspective. We
utilize app reviews, which are widely recognized as expressions of user
perceptions, to identify the ad costs concerned by users. Four types of ad
costs, i.e., number of ads, memory/CPU overhead, traffic usage, and bettery
consumption, have been discovered from user reviews. To verify whether
different ad integration schemes generate different ad costs, we first obtain
the commonly used ad schemes from 104 popular apps, and then design a framework
named IntelliAd to automatically measure the ad costs of each scheme. To
demonstrate whether these costs indeed influence users reactions, we finally
observe the correlations between the measured ad costs and the user
perceptions. We discover that the costs related to memory/CPU overhead and
battery consumption are more concerned by users, while the traffic usage is
less concerned by users in spite of its obvious variations among different
schemes in the experiments. Our experimental results provide the developers
with suggestions on better incorporating ads into apps and, meanwhile, ensuring
the user experience.
