Search engines are like public restrooms. They're only as safe and sanitary as the last people who used them.
For example, the "mosque at Ground Zero" became the most common way to search for information about a controversial Islamic center proposed two blocks from Ground Zero. It was neither a mosque nor at Ground Zero, but search engine optimization doesn't care about accuracy and so the search results reflect the most common perception. This perception is then reflexively reinforced because the search engine points anyone looking for more information to links with the "mosque at Ground Zero" phrase. And anyone wanting to get hits has to use some form of the phrase to get noticed.
There is no search engine janitor.
Poynter has more about this here.