6/18/2009: Computable Knowledge with Wolfram|Alpha
wolframalpha.com provides direct numerical answers to questions that can be computed using public data.
For example, 'wired magazine circulation' returns the answer 715,000.
It's a neat idea, but in order to be useful, it needs almost limitless data - otherwise, most questions go unanswered, and the user is better off going straight to a conventional search engine.
Here are a few example of simple tests I ran:
Wolfram|Alpha was announced with much fanfare, and the first month traffic was a very respectable 1,536,346 unique visitors, according to Compete.com. However, unless users are able to find the answers they are looking for, I believe they will quicky become frustrated and abandon the site.