It has been twelve years since Tim Berners-Lee threw up his hands and said "it's all crap, let's do it over" and set off to create the Semantic Web. We've got very little to show for it so far. I firmly believe the work Semantic Web technologists are pursuing is important and the concepts will inevitably be realized and I very much want to see this research become viable. But things are not moving fast enough and the tack semantic researchers are taking simply isn't working.
Semantic Web technology is marred in a chicken/egg paradox. The technologies are generally not useful unless they are adopted and implemented on a large scale and people are not willing to invest in implementing them unless they are useful. This is exacerbated by the fact that there are very high technology, business, and social barriers to implementing the Semantic Web.