No kidding. One serious case was back in 2011-12. A girl contacted me asking for help because this guy kept sending her PMs pressurizing her to join him for his BDSM sexting game play(? I suppose it was online only). She kept refusing and he would still insist in next PM. I was a fairly new mod back then and admins were away. The girl too was a noob and didn't know how to report a PM. She had taken screenshots of PMs and sent me images instead of the pm itself. So I couldn't get how severe the problem could be. Still I gave a warning to the guy and told him to stop sending her such PMs and told the girl to contact me if he persisted. But that girl stopped coming to NB. And to this day I suspect my warning resulted in some more threats. After some time another girl reported a few PMs. And these were even more full blown and I forwarded the report to Zise who immediately asked me to ban the guy permanently. I wish I had done that first time around but that was my first time encountering such a serious perv on NB. The guy wasn't a minor- his victim's profile ( at least these two girls) said they were. Zise said he had sent such messages to more girls though not all of them reported it.
When a grown up joins an anime site to find little girls to prey upon and cultivate them as a *** slave and indulge in BDSM then you know how much your kids need to be cautious while at internet.
Luckily we haven't had any other report of that kind since. Though I know another guy who befriended and got some minor girl trust him and talk to him via video chat and then uploaded it at you tube and then posted the video at NB. .. Girl 13- 14 year old. I haven't seen her since either. She used to be pretty active and chatty back then. I wonder if her family found out the video. She was in USA or Canada but her family was from South Asia. So if they did they would hardly be happy about it. ..
These two cases were too distinct because in both cases the pervy members were otherwise popular and if you talk to them normally you wouldn't easily get how far they could go.