Google's Quality raters Guidelines
 

http://static.googleusercontent.com/...guidelines.pdf

See the porn section on page 25-26 ... how they will assume certain keywords that may have porn intent go to non-porn pages. meaning make your keywords certain to contain porn if you want google to show that to the user.

Ex: spanking ---> non porn site
spanking lesbians with anal ----> porn site

This goes right along with the changes made to image search to clearly interpret user intent related to porn searches.

They're getting smarter about their image search. While crawlers still can't read images, you need to get more and more clever with the way you use SEO - depending on whether you want to hide your site in the mainstream or place it firmly in porn.

Makes sense. Someone searching sex for instance isn't necessarily searching for porn. Someone searching for sex videos on the other hand...probably porn.

I've though they've been doing that for years, just not very well..
https://www.google.com/search?q=creampies