I think the main reason why the semantic web has not become popular is a) Chicken and the egg problem. There are no search engines or aggregate sites that make

I think the main reason why the semantic web has not become popular is a) Chicken and the egg problem. There are no search engines or aggregate sites that make use of it. So we do not bother marking up our data. b) XML is very alien to most people, we need to implement the semantic web into graphical user interfaces! c) It's hard to sell the concept as it's hard to imagine the use cases. We somehow need to bootstrap by creating data and example services, people will want it once they see it.