They are too busy looking at titties or cocks

Something tells me you didn't read my comment.

Unless we want snapchat and other apps to require photo ID, how would snapchat actually know who is a child and who is an adult? Why did the parents not know or care that the kid had snapchat downloaded?

We had to walk a delicate line with our kids (2005-2017) when it came to interaction online. Never wanted them to feel like we were keeping them from experiencing the knowledge or social interaction the internet provided. But we also kept close tabs and paid special attention to specific behaviors. So if they were in their netbooks we’d make it a habit to walk behind them not to look but just to see what their reaction would be. Kids mostly know right from wrong and when they feel it “might” be wrong they try and hide it from their parents. If you pay attention you’ll see them “hiding” and that’s a sign to dig deeper. This way they maintain their privacy and any issues can be brought to light with them directly.

(Understand that the following will have specific details changed just for anonymity’s sake) Grooveshark was the first interaction we saw was troublesome. So we sat our daughter down and asked her direct why she was trying to hide her netbook from us seeing it and what had she been doing she felt she needed to hide? The alternative was to relinquish the netbook until she told us. Come to find out a friend of hers from school (female 2 years older) was trying to slowly convince her to lie to her parents and sneak off with her. Our daughter told us this because it scared her not because she would lose her access. We also stayed open and active with our kids indulging in the same things they were interested in (Minecraft, Guitar Hero, etc) regardless if it was explicitly something we enjoyed. So she didn’t lose access to Grooveshark because she really loved listening to music. We just kept an eye on it and she removed her friend from communication. We explained what she was likely attempting and her friend admitted to it. They’re not friends now but it never happened again.

Don’t get me wrong, we made tons of bad calls before we learned what worked. But the key to all of it is paying attention. Not hovering over them and stopping them from making mistakes. But watching the nuance of their interactions with everyone around them. If they start to get secretive then there is usually a reason. And it’s best to just talk to them about it. And if one conversation doesn’t do it then have multiple conversations. Listen to what they have to say and why they were being secretive. Works best when they’re not expecting it too (like in the middle of playing Minecraft together). Anyway that’s just IMHO.