Hanu Kommalapati with a nice comparison between the private and public clouds based on Economy of Scale and Quality of Service.
There has been lot of talk on the definition of Cloud Computing and the fundamental differences between public and private clouds in the architect and decision maker community. The definition I like for Cloud Computing is: “On-demand utility computing delivered through internet standards and protocols”. This allows the flexibility of various cloud types including Public Cloud, Private Cloud, and other hybrid variants which may fall in between. These definitions are similar to the web application deployment taxonomy: internet, intranet, and extranet segmented based on the scope of the target audience.