I don't know how the concept is treated on other languages, but on brazilian criminology we talk about a "black cipher", which is the amount of a certain crime which goes by without being ever investigated, let alone ending up on some sort of sanction. And the black cipher for pedophilia is absolutely huge.
It has been suggested time and time again that the preference of law enforcement for conducting huge operations, often desiring for the resulting media coverage (specially on crimes such as pedophilia), hinders and directs efforts and resources away from the daily enforcement which would be much more effective.
Not to mention sting operations are a form of entrapment and ilegal in many countries for giving the government the immoral option of deceiving for punishing a citizen, and giving the indictee the defense that there would have been no crime if there wasn't a government agent instigating it (and thus no harmful conduct was being commited).
