It sure beats instant coffee. A major change to Google's results page has created an intense interest in interfaces that provide immediate feedback. Google Instant, which updates search results as you type, inspired YouTube Instant, which many developers have emulated using a number of different APIs.
This past Valentine's Day, DuckDuckGo announced via Twitter that their search engine had "received over 1,000,000 direct searches yesterday for the first time ever!" A major accomplishment for a search engine that is essentially unknown. And this search engine has an API.