Mark Symonds, CEO of Plexus Systems, has written a good viewpoint piece for IndustryWeek in which he examine the nature of what is and isn't SaaS, and he calls "BS-aaS" on some so-called SaaS offerings.
Pointing out a key difference in some hosted, on-demand offerings, Symonds points out that true SaaS will have customers running off the same code base without worries about upgrades and without the need for locally installed software or hosting hardware but that "pretenders" often attempt to sell the same old client/server applications as SaaS merely by putting them in third-party hosts. He then offers suggestions for how to distinguish a true SaaS application from a pretender.
Got any thoughts about distinguishing SaaS from "BS-aaS"? Post 'em here.
Take a look at "True SaaS Delivers More Value" at http://www.iqnavigator.com/White_Papers.html, which details the elements of True SaaS offerings and how to tell them from the pretenders.