Can a hashtag be a protectable trademark? And when does use of another’s trademark in hashtags constitute infringement? Disagreement has arisen among the United States Patent and Trademark Office (“PTO”), the courts, and commentators about whether hashtags can be protected at all. A trademark, of course, is a source-identifier – a “word, name, symbol, or device, or any combination thereof” used “to identify and distinguish … goods, including a unique product, from those manufactured or sold by others and to indicate the source of the goods.” 15 U.S.C. § 1127(a).