The Sapir-Whorf Hypothesis postulates a link between thought and language: if you haven't got a word for a concept, you can't think about it; if you don't think about it, you won't invent a word for it. The term "Web 2.0" is a case in point. It was invented by a book publisher as a term to build a series of conferences around, and conceptualises the idea of Web sites that gain value by their users adding data to them. But the concept existed before the term: Ebay was already Web 2.0 in the era of Web 1.0. But now we have the term we can talk about it, and it becomes a structure in our minds, and in this case a movement has built up around it.