The social engagement of eWOM (electronic word-of-mouth) can reduce the threat of adverse selection in e-commerce. As studies that examine the social influence of eWOM are rare, the present work suggests the moderating effect of review or reviewer helpfulness and product type (experience or search goods) on the relationship between eWOM and product sales. The volume of eWOM, which is defined as the multiplication of the average length by the number of reviews, is shown to be moderated by review and reviewer helpfulness and search goods to affect product sales. Review ratings are moderated by reviewer helpfulness, and review extremity is positively (negatively) moderated by search (experience) goods and review helpfulness to affect product sales. As previous studies of differentiated sampling strategies that consider review helpfulness for predicting product sales using eWOM are lacking, this study compares the prediction power of business intelligence methods for different subsamples of products created according to high or low review and reviewer helpfulness levels. The subsample with high review or reviewer helpfulness demonstrates greater prediction performance than the subsample with low review or reviewer helpfulness when eWOM variables are used as predictors of product sales. Hence, preliminary filtering data preprocessing should consider review or reviewer helpfulness as a crucial criterion of the data quality. This will contribute to the sampling or preprocessing strategy used to predict product sales using eWOM.

Mobile social apps have experienced enormous growth as online personal networking media. Social exchange theory (for individual motivation), theories of collective action and social capital theory (for social capital) can be applied in order to understand how an individual’s behavior may exert effects on or receive influences from other users with regard to the continuance usage intention of mobile social apps. This study examines individual motivations and social capital affecting relationship quality in terms of trust in and satisfaction with mobile social apps and how these factors influence continuance usage intentions of mobile social apps. An online survey is used to collect 320 responses from users of mobile social apps. Our results indicate that promotional motivation and innovativeness affect relationship quality levels. Maintaining relational enhancement, social homogeneity, and social identity along with service usefulness have effects on the relationship quality level, which in turn affects continuance usage intention. Given the lack of studies regarding the application of the theories of collective action and social capital to gain a better understanding of continuance usage intentions, this study provides additional insight into how individual motivations and social capital affect continuous usage.