There's an interesting story in The Economist. This extract will tell you what it's about.

How well does the world wide web represent human language?
Linguists seek the underlying rules of how language works in the minds and mouths of its users. What actually sounds right and wrong to people, what they actually write and say, is the linguist's raw material.

But that raw material is surprisingly elusive. Getting people to speak naturally in a controlled study is hard. Linguists, however, are slowly coming to discover the joys of a free and searchable corpus of maybe 10 trillion words that is available to anyone with an internet connection: the world wide web.

For several reasons, though, researchers are wary about using the web in more formal research. ...

Well - this certainly works on here, doesn't it? How often do we google for usage examples?