Copycat brands try to entice consumers by imitating the trade-dress of leading brands. Recent research suggests that preferences for copycat brands relative to more differentiated brands are generally lower. That is, consumers tend to dislike such "imitation" brands, because of psychological reactance. Three experiments provide evidence in support of the counter hypothesis that preferences for copycats, rather than being generally negative, critically depend on consumers' uncertainty. When uncertainty about product quality is low, people dislike copycat brands, but this preference reverses when uncertainty is high - despite awareness of the imitation tactics being used. We speculate that this preference reversal occurs because the familiar feel of the copycat is interpreted positively when being uncertain, but negatively when being certain. This double-edged effect of brand similarity has implications for preference theory, consumer decision-making, and managerial practice. © 2013 Elsevier B.V.