Collaborative initiatives in the sharing economy involve peer-to-peer relationships, often mediated by an online platform. The very nature of such horizontal relationships, in which the service is likely to be delivered by a non-professional provider, introduces a new context for service evaluations. Exchanges between strangers create uncertainty about the outcomes and the way in which the service will be delivered. Due to such extreme heterogeneity, consumers have difficulties in delineating their expectations. In addition, collaborative initiatives may feature different formats, ranging from pure sharing characterized by love, no need for reciprocity, and the irrelevance of money; to pure exchanges featuring impersonality, reciprocity, and monetary compensations. This chapter seeks to increase understanding of these effects by investigating consumer (dis)satisfaction processes in the sharing economy. By combining an analysis of online archival data with critical incident techniques, the chapter identifies several features that distinguish collaborative exchanges from traditional ones and provides an alternative framework for depicting the evaluation process associated with collaborative services.