Web 1.0: People connecting to the Web (P2W?). i.e. “Wow, I’m on the Internet!”
Web 2.0: People connecting to other People (P2P?) i.e. Social networking, wikis, collaboration, sharing.
Web 3.0: Web apps connecting to web apps on behalf of People to enrich online experiences (W2W?) i.e. The Symantec Web, the Geospatial Web, application awareness of context, autonomy from the browser.
Web 4.0: The web becomes sentient, rises up, conquers the world and enslaves the human race? (W>P?)
I wrote this in 2007. Still stands up IMO.