CMP claims a right to exclusively use the term web 2.0, kind of like a trademark, and they've sent O'Reilly a cease and desist order regarding the matter. As usual, Russ has a great write-up on it, including scans of the letter itself. My take? Two words:
Puh Leeze.
Trademark law, I'm no expert. But I do know this. If you don't enforce your trademark rights early and often, you are going to lose in court. CMP doesn't have a chance here, because O'Reilly and everybody else have using this term for many, many months without so much as a peep (that I know of) from CMP. Sorry guys.
