Jens Thraenhart had this descriptive visual on his blog
it shows the essential difference between web 1.0 and web 2.0 for those who care about definitions.
In my opinion the key element is the increasing cloud of “collective intelligence” which is really the main difference as the web has enabled and facilitated two way conversations or dialog rather than the first iteration of one way communications inherited from the offline world. Remember ever writing a letter to the editor of a newspaper or magazine, put it in an envelope, affix stamp and then bring it to the post office or mailbox. Compare that to today’s link on New York Times articles offering you to “share” it or even email the author.
The sooner corporations and organizations of all kinds realize that true dialog with customers is the reality and encourage it without corporate b.s. filters the better.
It doesn’t really matter what label we put to this new environment the key is to understand the essence.