ProgrammableWeb.com/ - The Web as Platform

What is does the "Web as Platform" mean?
Historically, some types of software like desktop operating systems have been called 'platforms' because through their APIs they provide the foundation on which other programs are built. The phrase 'web as platform' refers to fact that as web sites start providing their own APIs, they too are becoming a platform on which other programs can be built. Sometimes this is also referred to as the Internet Operating System.