As software-as-a-service (SaaS) continues to increase in popularity across a growing range of application areas, many firms still wonder what differentiates SaaS from other deployment models like traditional hosting and how to decide whether it will fit their needs. At the same time, as some SaaS buyers express concerns over the traditional multi-tenancy setup, SaaS providers are evolving their models. Sourcing teams evaluating SaaS opportunities need to understand how SaaS options have evolved in order to make the best decisions for their firms.