German Heise writes (adult language ahead):

<<In a sudden turn of events concerning the battle for the protection of young people from exposure to erotic content on the internet, Huch Medien GmbH has filed for expedited proceedings at the first-instance District Court of Frankfurt to force Arcor to block Google.de and Google.com in order to prevent pornographic texts from being displayed without age confirmation. Huch itself operates the erotic site Amateurstar.de and says it will not simply sit back and watch Google's image search display hundreds of pornographic images for users of all ages who enter such terms as "porn", "fuck", or "oral sex". Huch claims that even images of "clearly prohibited animal pornography" can be viewed via the search engine.>>
http://www.heise.de/english/newsticker/news/100074

[ Via http://searchengineland.com/071205-085002.php]

Well, to see those images you need to disable Safe Search. By default, Safe Search is set to moderate, so you'll see very few adult images. Google could ask your age, but you could also lie (YouTube has an age conformation feature).

And what's interesting to note is that Amateurstar.de, the site of the one attacking Google/ Arcor, starts with a NSFW splash page.

If they ran tests and found offensive material, they could always submit a form to have those image removed.

https://www.google.com/webmasters/tools/removals?pli=1

Occasionally offensive images will show up under the 'moderate' SafeSearch setting, if you feel so inclined, just follow the few extra steps to report it and Google acts pretty quickly to get it resolved.