This will go down as the year the second internet mania was born. It was the year when Google paid $1.65bn for YouTube, the site for amateur videos, less than 12 months after YouTube was launched; when MySpace attracted more page views in the US than Yahoo; when Wikipedia, the online encyclopedia written by volunteers, became one of the 10 most-visited websites; and when Time magazine made “You” (in praise of those who use websites like these for self-expression) its “Person of the Year”.

The race is now on to find the next upstart website capable of forging a mass audience from this outpouring of so-called user-generated content, and to spot the next broad trend that will shape how millions of people use the online medium. Five years ago, who would have expected blogging and social networking to enter the mainstream?