From the Google Blog:
Answer highlighting in search results
Consider the example, [empire state height]. With today’s improvements, the answer —1250 ft, or 381 m — is highlighted right in the search result:
This might be cool for Wikipedia, but it totally screws every other website owner.
If you have a website that deals with anything Google’s algorithm has decided is a “fact” then watch out, your traffic is about to drop. Google’s destroyed a lot of niche online markets but this is a broad attack against all sites.
The future of this feature is that you never have to leave Google at all.