The issue Reddit faces is simple: If they want to control content, they need the tools to control content. If they lack the tools to control content, they must rely on social engineering. I would go as far as saying anything with nudity should be well-firewalled deep into Reddit. Require a credit card at least. But the twin problems with this are (1) see previous comment about tools (2) 80% of Reddit's traffic, as of 2011 at least, was porn search. And yes. "Jailbait" was one of the principal search terms. There's a world of difference between the traffic stats Reddit advertises and what a paid report from any of the CPM sites will give you. Reddit is a porn haven.
Knew a guy in charge of "the internet" for all of one of the big 5 studios (Sony, Warner, Universal, Disney, Paramount). Bigtime redditor. Tried to sell said same studio on Reddit. Said same studio paid for the actual traffic reports, as opposed to the stuff Reddit usually hypes. Reddit is radioactive with porn.