Extra Korea pointed out a case involving wonjo gyoje, video, and blackmail reported in the Korea Times. This NoCut News article has more information:
Police have arrested men for spreading a sex video of a Wonjo Gyoje encounter with a middle school student. Seoul Mapo Police have booked without detaining three men including 39 year old Mr. Yu and and 39 year old Mr. Jeong for on charges of sexually assaulting and blackmailing a minor.
According to police, Mr. Yu met middle school student ‘A’, who was then 14, via chatting on Buddy Buddy in October 2007 and paid her between 150,000 and 200,000 for sex. ‘A’ continued to meet Mr. Yu and had group sex with him and Mr. Jeong, who recorded encounters with a digital camera.
‘A’ continued to meet the men for two years but recently when she didn’t meet them they threatened to spread the sex video on the internet and did in fact post it at a pornographic internet cafe.I'm sure as long as there's been wonjo gyoje (the first cases were prosecuted in the fall of 1998), there's been guys videoing the encounters. This case from March 2000 tells the story of a 40 year old visiting professor from Gangnam’s Dogok-dong working at D University who was arrested for paying two girls on two occasions (including an unemployed 17 year old) 30,000 to 50,000 won for sex and videotaping the encounters. He also exchanged bags and clothes for sex with university students. As for why, he told police that his wife had hurt her back and they couldn’t enjoy a normal sex life, and his curiosity led him to meet teenage girls. As for the videos, he just wanted to be able to watch the encounters later. The article also points out that at that time the places where many 'meetings' were arranged were 'phone rooms,' which still exist today, but have mostly been replaced by the internet.
‘A’s face was visible in the video put up on the cafe and to remove it she suffered a sexual assault.
‘Yu’ and the others stated that they made the video because they were bored.
A police official said the suspects are all married men and they fed ‘A’ alcohol when shooting videos, and that around 20 videos or pictures were confiscated from the men.
This article, from June, says that there has been a huge increase in lewd 'selca' videos made by teens imitating adults and how safeguards to filter out such content on the internet aren't working. I don't feel like pulling the stats out of that article so much - I just liked the image that accompanied it.
The arrival of this phone will likely do nothing to stem the increase in such selca videos, but it may well improve their composition.
As for cases involving underage boys - which are not referred to in the media as wonjo gyoje but as prostitution or molestation - in this case from 2006, a 40 year old man was found on a prostitution site to have met teenage boys and when police arrested him found 2000 photos and 100 videos of 100 boys (including 10 elementary school students) that he had bought sex from or molested. He admitted to this with around 150 underage boys, but a police official pointed out that he didn't have homosexual relations with adults, he just had a compulsion to go after minors. Oddly enough, several cases of men paying teenage boys for sex were reported in July 2008, and at that time a Ministry of Health, Welfare and Family Affairs official also pointed out that the men weren't necessarily gay, they just "had a sexual appetite they could not control." Perhaps there's a guidebook handed out to public agencies we don't know about...