  Evolving software with an increasing number of features is harder to
understand and thus harder to use. Software release planning has been concerned
with planning these additions. Moreover, software of increasing size takes more
effort to be maintained. In the domain of mobile apps, too much functionality
can easily impact usability, maintainability, and resource consumption. Hence,
it is important to understand the extent to which the law of continuous growth
applies to mobile apps. Previous work showed that the deletion of functionality
is common and sometimes driven by user reviews. However, it is not known if
these deletions are visible or important to the app users. In this study, we
performed a survey study with 297 mobile app users to understand the
significance of functionality deletion for them. Our results showed that for
the majority of users, the deletion of features corresponds with negative
sentiments and change in usage and even churn. Motivated by these preliminary
results, we propose RADIATION to input user reviews and recommend if any
functionality should be deleted from an app's User Interface (UI). We evaluate
RADIATION using historical data and surveying developers' opinions. From the
analysis of 190,062 reviews from 115 randomly selected apps, we show that
RADIATION can recommend functionality deletion with an average F-Score of 74%
and if sufficiently many negative user reviews suggest so.
