But there's no reason that search engines should be limited to trivial searches of public data. A modern search engine needs to be able to handle situations like:
* User has a reservation at a local restaurant, so they ask [where's lunch] and want to receive the time and location of their reservation. And they want driving directions, unless they don't own a car, in which case they want directions from the nearest public transport.
* User just got back from Hawaii and wants to show their coworkers a photo they took of a cool wave. So they search for [wave picture] and want the picture they took to be in their search results.
* User is writing a PhD thesis on tree rings and found a useful article last month, but now they want to cite it and can't remember what it was called. So they search for [article about tree rings] and want that particular article to be the first result.
In other words, the 2001 model of a search engine as "grep for the web" is far behind what people expect in 2013.