Google's autocomplete filter now censors certain search terms. While this may or may not be successful at stopping "piracy", it certainly manages to filter wikipedia pages on these topics.
See here, and note the top hit for their example: http://torrentfreak.com/why-is-megaupload-still-censored-by-googles-piracy-f...
I've also tested a few of the knwn terms myself.
sincerely, Kim Bruning