Apparently Web 2.0 is now a trademark - at least that's what CMP, acting on behalf of, amongst others, O'Reilly, would like us to believe. There's a good run down of the issues here, but the heart of the matter is that another company is running a conference with Web 2.0 in the title and CMP don't like it. Web 2.0 is a phrase that is used just about everywhere to refer to a variety of technologies and websites, but I hardly think it is trademark material.