Influencer marketing has become central to brand promotion, yet it confronts firms with a fundamental trade-off between control and authenticity. While brands can govern paid collaborations, influence often extends beyond these boundaries, limiting firms’ ability to fully shape where messages appear and how they are framed. Using comprehensive data that combine influencer activity with brand sales across direct-to-consumer and reseller channels, we examine how influencer identity (paid vs. unpaid), platform choice (primary vs. non-primary), and message alignment (high vs. low alignment with brand guidelines) jointly shape brand sales outcomes. Our results show that influencer marketing does not uniformly translate into sustained brand gains, certain forms of influencer activity generate short-lived performance improvements, while others offer limited or even negative returns. Consistent with the control-authenticity tension, tighter message alignment does not uniformly enhance effectiveness and, outside paid collaborations on the primary platform, can reduce it. Moreover, platform choice further determines how and where sales responses emerge, underscoring the importance of interpreting influencer impact beyond a single channel. Together, these findings highlight the strategic importance of deciding who communicates for the brand, where influence unfolds, and how closely influencer messaging aligns with firms’ strategic intent.