The development of e-commerce relies upon customer usage intentions, and IS researchers have examined usage intentions toward various online e-commerce systems. However, these systems have been studied in prior works independently rather than comprehensively. In order to pursue better measures for predicting and explaining B2C e-finance and some other major e-commerce adoptions for customers, we conducted a comparison analysis across different online systems to advance the understanding of the adoption factors and their linkage to customer behavior. Refining from Perceived Risk Theory and existing studies, specific risk facets, customer characteristics and system characteristics were operationalized and integrated within the Technology Acceptance Model (TAM) resulting in a proposed e-finance and other e-commerce system adoption model.