Dominique M. Hanssens is Bud Knapp Professor of Marketing, Anderson School of Management, University of California, Los Angeles (e-mail: dominique.hanssens@anderson.ucla.edu). Roland T. Rust is Distinguished University Professor, David Bruce Smith Chair in Marketing, and Chair of the Department of Marketing, Robert H. Smith School of Business, University of Maryland (e-mail: rrust@rhsmith.umd.e...