Web 2.0 is generally referred to as the next generation of web applications. Many are open source and free. Some examples of Web 2.0 applications are Flickr, Pandora, and Google Maps. The folks over at O'Reilly and CMP entered into a partnership agreement to offer Web 2.0 Conferences. The folks at CMP applied for a special mark (a flavor of trademark) for the Web 2.0 Conference. Another firm it@cork in Ireland wanted to host a half day conference with the words Web 2.0 included.
A cease and desist letter was issued not to use the phrase Web 2.0 and the blogoshpere reacted quickly and ruthlessly. The situation grew in a day to be one of the top gaining links on bloglines.
Tim O'Reilly responded to the controversy but it took a few days. He was actually on vacation with his family with limited media access. One of the great (and bad) things about a blog is that the message can be delivered quickly. The firestorm has cooled a bit but it remains to be seen if the phrase Web 2.0 is off limits.