I've blogged here several times about the confusion growing around the use of "cloud" versus "SaaS" terminology when describing software offerings and the fact that just because an application is hosted "in the cloud" does not necessarily make it SaaS (multi-tenant) - even if it's "virtualized."
It’s not an easy transition for legacy software companies to make from being a provider of conventional single-tenant software products to being a true multi-tenant SaaS vendor. It’s not just about the technology and re-building offerings. It means re-building every aspect of the company – marketing, sales, pricing, fulfillment, support and services, go-to-market strategy, channels, processes, organization, skills, culture etc. The very DNA of the company must change. And it means painfully cannibalizing product maintenance revenue streams (the vendor's "cash cow") while making the transition to SaaS. It is hard work and therefore no surprise that some legacy vendors are trying to take shortcuts in order to ride the wave of SaaS and cloud computing popularity by offering "cloud versions" of their conventional software products ala the ASP hosting model of the 90's.
So as a consumer, how can you tell if your vendor is truly SaaS? After all, if your vendor is "in the cloud" and charges on a "subscription" basis then they must be SaaS right? Caveat Emptor - read my article in eWeek for tips you can use to help find out if what you’re buying is really SaaS or an ASP cloaked in the cloud.