<p>I disagree (disclosure: I posted the question you're using as an example).</p>

<p>It is certainly annoying to have duplicate questions within a StackExchange, but if the question is original and on-topic, I don't see the problem in having it here.</p>

<p>Remember that the StackExchange engine has an advantage over random Google search results and Wikipedia entries; namely, that the answers are voted upon by knowledgeable users, so that incorrect (or unhelpful) material is less likely to appear at the top. With Wikipedia, it can be harder to know whether or not an entry is correct.</p>
