The authors thank Blue Mango Interactive and the Dutch State Lottery for providing the data; the views expressed in this paper, however, do not necessarily reflect those of Bluemango or the Dutch State Lottery. The authors thank Menno Zevenbergen and Pieter van Geel for stimulating discussions and useful comments; without them, this project would not have been possible. They also thank Senior Editor Puneet Manchanda, the associate editor Günter Hitsch, two anonymous referees, Jean-Pierre Dubé, Ulrich Doraszelski, Eric French, Ulrich Kaiser, Carl Mela, Peter Newberry, Martin Peitz, Pasquale Schiraldi, Stephan Seiler, Andrey Simonov, Rik Pieters, Frank Verboven, Ken Wilbur, Joachim Winter, participants of a seminar in Oxford, participants at eBay in San José, and participants of the 2015 Media Economics Workshop in Stellenbosch, the 2016 meeting of the Industrial Organization group of the Verein für Socialpolitik, the 2016 Digital Marketing Conference at Stanford, the 2017 Center for Economic and Policy Research Conference on Applied Industrial Organization, the 2018 European Economic Association/Econometric Society European Meeting in Cologne, and the 2019 Choice Symposium in Chesapeake Bay for their for comments and suggestions.