This paper tests whether geocaching, a real-world treasure hunt activity using GPS devices and clues provided by other participants, can be modeled as an addictive pursuit. Using over 36 million online activity logs posted by more than 675,000 users in 2010, we find strong evidence that the activity follows a pattern of rational addiction. The result has implications not only for this activity, but for a host of other social activities that increasingly blur the edges between online and real-world communities and activities.