Content moderation is one of the things that CrowdFlower does really well -- and yes, you can have workers search for adult content (At least on Mechanical Turk. I'm not sure about our other labor pools. In any case, you can definitely use CrowdFlower for filtering out adult content.)

You'll probably want to make sure your job description mentions that, though!

(I'm a front-end developer for CrowdFlower. I don't represent the company's views. Except in regards to bacon. I represent those.)