In this paper, we examine a previously ignored yet important research question concerning the online user reviews: Why do some reviews not receive any votes on their helpfulness, while other reviews receive many votes? The helpfulness voting mechanism works effectively only when online user reviews receive helpfulness votes. We address this question by investigating the impact of various characteristics of online user reviews on the number of helpfulness votes that reviews receive. We categorize characteristics of online reviews into three types, namely, basic, stylistic and semantic. Text mining techniques and ordinal logistic regression models are employed to investigate more than 3400 online reviews of 87 different software programs from CNET Download.com. A number of practical and research implications can be derived from this study.