Computerworld: IaaS vs. PaaS vs. SaaS
Several different flavors have sprung up in cloud computing and each has their pros and cons. Add to these the plethora of vendor-created acronyms and it can be confusing to figure out the best option.
The three primary types of cloud computing are IaaS, PaaS and SaaS - infrastructure, platform and software as a service, respectively. When you take a closer look, you'll see that what will decide this argument are your own company's needs and comfort level.
These services are made possible by virtualization, the ubiquity of high-speed networks and the capabilities of today's browsers. With these things in place, it becomes less necessary to own your own infrastructure, or even to own your own software. You can get what you need from the cloud, as you need it.
More of the Computerworld article from Jeff Caruso