I think of a disruptive technology is something that changes the way people interact. This includes changing how people create knowledge and organize themselves into groups.
McLuhan said the medium is the message. The Web 2.0 (for lack of a better term) world has brought with it a message that is egalitarian when it comes to knowledge creation. The authority of the book, tv news show, and newspaper are undermined by the fact that anyone can now create and distribute. The meaning of authorship changes as now anyone can copy, remix, re-edit, add, subtract.
Each conversation online enforces the non-authoritarian view. This is the message of the medium. No matter what is being said, this same message is coming across. I practically live online. I just this week have realized that I really bought into the medium’s message without realizing where the message was coming from, exactly. I was hearing the message constantly without realizing it. How much did it affect my thinking without me knowing it? I paid attention to the content being transmitted by the web, without realizing consciously the message it was repeatedly sending me. This is not to say that I believe I have been brainwashed anymore than someone who does not buy into this worldview has been brainwashed by reading books. In both cases, there may be a little brainwashing going on.