Self-Appointed Brand Managers
The second explanation is in some respects the reverse of the upset customers explanation. It is possible that these customers are acting as “self-appointed brand managers”. They are loyal to the brand and want an avenue to provide feedback to the company about how to improve its products. They will even do so on products they have not purchased.9
We can further investigate this explanation by asking: when would a self-appointed brand manager be most likely to write a review? One possibility is that customers are more likely to react when they see a product that they did not expect. If a customer, who has only purchased women’s apparel from the firm, is browsing the firm’s website and notices that the firm now sells pet products (for example), this may prompt the self-appointed brand managers to provide feedback by clicking the button inviting a review. Why would self-appointed brand managers be more likely to write a negative review? The French have a phrase that may help to answer this question: “Qui aime bien châtie bien,” which translates (approximately) to “your best friends are your hardest critics.” We investigated whether there is a relationship between the number of items that customers have purchased and the reviewers’ product ratings. The pair-wise correlation between a reviewer’s average product rating and the number of items purchased is 0.048 (p < 0.01). In other words, the most loyal customers are the most negative reviewers.
10
Prior Units Index: The total number of units of this item sold by the firm in the year before the date of the review. At the request of the retailer we index this measure by setting the average to 100% for the reviews with a prior transaction. We investigate this possibility by calculating the following measures:
Niche Items: Equal to one if Prior Units is in the bottom 10% of items with reviews, and equal to zero otherwise.
Very Niche Items: Equal to one if Prior Units is in the bottom 1% of items with reviews, and equal to zero otherwise.
Product Age: Number of years between the date of the review and the date the item was first sold.
New Item: Equal to one if Product Age is less than 2 years and equal to zero otherwise.
New Category: Equal to one if the maximum Product Age in the product category is less than 2 years, and equal to zero otherwise

In the Table 9 we report the average of each measure for reviews with and without prior transactions. The findings reveal large (and highly significant) differences on all of these measures. Reviews without a
prior transaction are more likely to be written for items that were introduced recently. They also tend to be niche items with relatively small sales volumes. These findings are all consistent with the prediction that customers are more likely to provide feedback on items they had not purchased when they see the firm selling a product that they did not expect to see.

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