Anomalous Reviews Owing to Referral Incentive.

In an online review system, a user writes a review with the intention of helping fellow consumers (i.e. the readers) to make informed decisions. However, product owners often provide incentives (e.g. coupons, bonus points, referral rewards) to the writers, motivating the writing of biased reviews. These biased reviews, while beneficial for both writers and product owners, pollute the review space and destroy readers' trust significantly. In this paper, we analyze incentivized reviews in the Google Play store and identify a wide range of anomalous review types such as copying, spamming, advertising, and hidden-beneficiary reviews. We also find an increasing trend in the number of apps being targeted by abusers, which, if continued, will render review systems as crowd advertising platforms rather than an unbiased source of helpful information.