There has been extensive research into friend-oriented and professional social networking websites, but relatively little work on passion-oriented sites designed to connect strangers around a shared passion. In this study, we extend the work on passion-oriented social networking through an examination of pet-oriented social networks. We address two questions. First, do people interacting in semi-anonymous passion-oriented social networks behave in observably different ways from users in friend-oriented networks? Second, do groups that, on the surface, appear quite similar (i.e. dog and cat owners) use the passion-oriented networks in significantly different ways? Our results show that passionoriented networking behavior is significantly different from that on friend-oriented networks and that despite the apparent similarities, dog and cat owners use these sites quite differently. We discuss the implications these results have theoretically for understanding passionoriented social...