Are there any good ML algorithms for detecting porn at all? I tried to implement the standard "pink detector" with mixed results.
A funny idea I had was to reverse the whole system - feed UGC content of a site that's supposed to be SFW into a porn site which is definitely NSFW, one that has lots of thumbnails. The ones that don't get any clicks to enlarge probably aren't porn and can pass the test :)
See also: SFW porn - where other images are super imposed on top of real porn. It's hilarious, but is it really SFW? You decide. http://www.reddit.com/r/sfwporn