Marketing has often stressed the importance of targeting firm communications to consumers who embrace and propagate trends. However, little is known about whether early trend propagators are indeed responsive to firm-sponsored messages. To explore this question, we use data from two field tests conducted by a charity and an emerging fashion firm on the micro-blogging service Twitter. On Twitter, `promoted tweets' allow advertisers to target individuals based on the content of their recent postings. Every day, Twitter identifies which topics are newly popular among Twitter users. In the field tests, the charity and the fashion firm targeted ads at consumers who embraced a Twitter trend early on in its life-cycle by posting about it, and compared their behavior to that of consumers who only embraced the trend later on. Throughout both field tests, we consistently find that individuals who embraced non-commercial trends early are less responsive to advertising than consumers who embraced trends later on. One explanation is that early trend propagators strive more than others to make their own unguided choices, and have little motivation to engage with commercially sponsored messages. We exploit differences between non-commercial and commercially sponsored trends, as well as variations in the promoted advertising messages, to provide suggestive evidence that supports this mechanism.