As someone who has been covering cloud computing for several years, I understand the community's fondness for definition debates. However, the reality is that most business-side people think of SaaS as cloud. They don't care about NIST definitions, nor do they want to debate them. They want speed -- and whether SaaS is cloud by your definition or not, SaaS has been the earliest exposure to cloud agility that many of the business side people have had. I would say let's stop worrying about definitions -- we are capable of explaining SaaS, IaaS, and PaaS differences. I have no problem lumping them all under the umbrella term of "cloud computing." By the way, I don't see why something must be multi-tenant to be cloud.