Fred Wilson, principal, Union Square Ventures:
The dream of the semantic web has been upon us for quite a while now. There have been hundreds of academic research projects, hundreds of approaches, and hundreds of startups working in this space. We have several in our portfolio like Adaptive Blue, Zemanta, Outside.in, Infongen, and one more we have not yet announced.

But this is a hard problem to solve and I don't see a single clear path to getting it solved. And what's interesting to note is that the most ambitious approaches have largely been failures. If anything, the more pedestrian approaches are showing more promise.

Complete blog post