This study examines how tourists experience authenticity and the ethics of "hill tribe" trekking in northern Thailand, and what they learn as a result of their touristic encounters. A "netnography" methodology was used to analyze on-line data from travelers’ touristic encounters with highland people in two sites. The first was the on-line reviews, blogs, and videos of travelers’ experiences in Baan Tong Luang, a multi-ethnic "hill tribe village" tourist attraction outside of Chiang Mai. The second was the blog and video reviews of visitors to three exemplary "community-based tourism" highland village sites. Findings show a variety of complex understandings of authenticity, both "objective" and "constructivist." For community-based tourism reviewers in particular, authenticity was understood as a hybrid, fluid concept which derived from meanings ascribed to objects, practices, and place; personal relationships with hosts; and opportunities for cultural learning afforded visitors.