What I take from the video is that Semantic Search will better understand a word or set of words like "Fluke" and the results will show links to a "Fish" and not results that include links to the movie "Fluke" about a dog.. Google's search engine will better understand a search querie based on Metawebs technology and show you more targeted results.
I'm interested how this is going to effect Long Tail Keywords that can have many meanings. Internet Marketers and webmasters looking to rank higher for Long tail keywords and can benefit from SEO with the new Semantic search by further defining what they mean by tagging Entities with the Metaweb technology.
If you are using compound words like "Notebook" Google already recognizes that most people are searching for "Notebook" Computers and not about Notebooks for writing in. I think when you get to the Semantic Search just like now you may have a hard time ranking for that keyword, and if you have a site that sells Notebooks for school kids, that keyword will be very difficult to rank for. However I do believe with Google tracking your "cookies" and based on your profile they can send you more targeted results for the right meaning.
I searched for Keywords that have the same letters like "dennis" and "Sinned" and Google has no problem showing results that are the correct results for their respective English meanings. I wonder what google is going to do for these kinds of words that are meant for foreign websites and they are read from right to left. This why Google has Search Engine results and web page evaluators that are currently classifying every page on the web to make search queries are more relevant for Top Level Domains and such.
Long Tail Keywords
Usually it is easier to rank for Long Tail Keywords and the traffic is more targeted. With Semantic Search I think they should be descriptive and the results will be more defined and data driven. Use the MetaWeb technology to your advantage and build a website with products and services including their data for a better user experience and achieve better rankings for pages that have unique useful information.
In closing I think Entities are a good idea and are driven by human results to build a more intuitive search experience. Search Engines are constantly modifying their algorithms so not only no-one may game the system but to serve up more relevant and targeted results defined by their own users.
I would head on over to my profile on Freebase.com which is Metawebs database for its new Search technology and start defining your entities to help your brand and SEO efforts.