To be successful and sustainable, peer-to-peer sharing systems need their participants to actively provide under-utilized resources, from spare rooms and cars to expertise and time. The goal of this paper is to compare the effectiveness of different incentive strategies in motivating people to share their resources. In particular, we examined five strategies: altruism, money, gifting, experience, and reciprocity. To compare the five strategies, we conducted two studies in the context of a network hospitality service - Couchsurfing. The first study was a survey where we asked hypothetical questions. The second study was a field study where we tested people’s actual responses to the different incentive strategies. Results from the two studies diverge. The survey study suggests that people are averse to all compensations. However, the field study suggests that men are motivated by compensation strategies while women still protest them.