In December 2008 a US court ordered Google to remove a long list of sites selling term papers from its search listings.
Although this may seem like a good thing on the surface, lots of universities use Google to check submitted papers for plagiarism. If the sites have been removed from Google, the plagiarism checks will not work any more.
Here are the court documents on Chilling Effects.
And it seems Google has been censoring the 4chan /b/-tards for some time.