Let's follow some simple steps: open you favorite browser, type in the address bar www.google.com and hit enter. Type "sex" in the search box and press search. Analyze the results. Quite impressive, only ONE site with detailed content about this word!
What happened with all that adult content? Well, Black Hat SEO posted a message saying that Google decided to filter all the adult and explicit content, so you won't get too many results in the top ten sites provided after a search.
So, after this process, it seems like the word "porn" will return only 3 explicit sites of 10, "sex" - 1 out of 10, "f***ing" - no porn in top ten and many other sex related words.
You'll also note that typing "anal sex", "teen sex" or "lesbian sex" will get not adult content in the top 30 sites displayed by Google.
In Webmaster Guidelines Google sustains that NO site with adult or explicit material will be indexed by its search engine but this decision is a huge disasters for a lot of web developers. Imagine that relegating your site will reduce your revenues and visitors, Google being one of the most important sources for obtaining popularity.
So, if you're porn addicted and Google's decision get you nervous, let me offer you a search hint: try searching for any word by placing the term "free" before them. You'll get interesting results
Free Porn on Google!
... so hot right now