Hashtags are trending, and not just on social media. By 2016, producers had federally registered hundreds of hashtags as trademarks and asserted exclusive rights in thousands of others. But by failing to pay close attention to context and consumer perception, the USPTO may have overlooked issues that render many hashtag trademarks (“tagmarks”) unregistrable. This article provides a history and taxonomy of hashtags and explores the protectability problems that plague tagmarks. Rather than sweeping generalizations about their status, tagmarks require nuanced analysis that takes into account their use, distinctiveness, and history in order to more accurately determine whether and when they merit protection as marks. To strike a better balance among the competing trademark concerns of consumer protection, producer reward, and speech, the USPTO should revise its examining procedures to mandate that every tagmark be categorized as “primarily merely a hashtag” until an applicant can establish that its mark actually functions as a source indicator.