How do people come to know that there is an encyclopedia?
In previous times, people (maybe) learned at school that there exist encyclopedias, what they are good for and where to find them. The publishers on their hand tried to reach as many people and also convince them to buy an encyclopedia.
How appalling that this is totally history by now, because of two internet giants which rose at the eve of the new millennium. Nowadays, pupils (and adults alike) open their web browser and often find Google pre-installed as the start page. When they ‘google’ for something, a Wikipedia article is almost always among the first five search hits. It is absolutely unnecessary that a teacher tells them ‘where to find the encyclopedia’. 
Andrew Lih in The Wikipedia Revolution recalls a case from April 2004, when antisemites had manipulated Google in a way that searches for ‘jew’ produced an antisemitic site at the top of the search. A site appears at the top if many other sites link to it. So internet activists asked people to link to another site, to beat the antisemites with their own weapon. The suitable site was Wikipedia because of its neutral point of view. 
Also Wikipedia itself became a victim of Google manipulation. It is legal and even legitimate to create a new site and use Wikipedia content there, so some people created Wikipedia ‘clones’ with adverts. Normally nobody would have looked at these clones, but some clone owners were capable enough to manipulate the Google search. Around 2005 there was a period when it was difficult to find the Wikipedia article among all those clones; after Google improved its PageRank, this problem became history too.
Some people even speak about a symbiosis between Google and Wikipedia, although it is not clear what the benefit for Google would be. On the contrary, Google is unhappy about the fact that for about one-third of the search hits go to Wikipedia articles – meaning, pages without (Google) adverts. So Google came up in 2008 with a knowledge platform of its own, Google Knol.
The media liked to present Knol as a Wikipedia killer that wants to avoid the flaws of Wikipedia. Knol wishes people to write under their real name, that they can own an article, are not bound to encyclopedic rules, and can make money per page views.
Of course, Knol came into existence when there was already a strong competitor (Wikipedia) on the market. But the main reason for the very limited success of Knol is more inherent: Knol is just another one of many places for single authors to publish, without control by anyone. Nobody at Google checks whether the authors really are the experts and professors they claim to be.
Anyhow, the intimate relationship between Google and Wikipedia will probably remain for a long time. A friend of mine once explained to me how he proceeds on the web. The retired archivist googles, and usually comes to Wikipedia, and then reads the article and maybe clicks on an internal link. And when he wants to look-up something else, he does not use the Wikipedia search (of which he doesn’t know at all) – he clicks the home button of his web browser and googles again.
 Andrew Lih: The Wikipedia Revolution, Hyperion books, 2009, p. 115.
 Andrew Lih: The Wikipedia Revolution, Hyperion books, 2009, p. 115, pp. 202-204.