First of all, we at Radar Networks are NOT building a new search engine to compete with Google, like Powerset and TextDigger are doing -- so we're not competing with them. Companies like Powerset and TextDigger are working on natural language search. Natural language search is not equivalent to the Semantic Web, although the Semantic Web can certainly help that process.

Companies working specifically on natural language search are making use of semantics, but at the word-level only. They use networks of words that are linked to synonyms, antonyms, homonyms and other variations. These are sometimes called semantic networks. Based on these networks of word meanings, they can understand the meaning of various words and expressions.

Interesting to see where they are going. Also a good overview of what the Semantic Web is and isn't vis a vis Web 2.0 (already hate that designation, but...)