Software as a Service and Cloud Computing

I've been doing a little research recently into Software as a Service (SaaS) and Cloud Computing, and have come across a couple of interesting articles. A couple of weeks ago, The Economist ran a special report on the evolution of Corporate IT (here, or in PDF). Tim O'Reilly posted a concise but interesting post on the O'Reilly Radar about Web 2.0 and Cloud Computing.