@AC with the 16 year old
If he has a PC in his room, it is because you allow it.
If that PC has internet access, it is because you allow it.
You - in effect - declare "I have considered the risks of unaccompanied internet access and have decided in my view that they are small enough to allow it".
You will live with the consequences of those decisions.
I do not need to understand "what it's like having a 14-16 year old, computer literate, `young adult` in the house". It's hard, and for the trials and tribulations it brings, I hope he goes on to make you very proud. However, the state cannot make the internet safer. The technology companies cannot make the internet safer. The only people who can reliably and effectively control a child's online life is that child's parents. That is the nature of the network. You may not like that, but it is true.
My parents knew what I was up to, what I could get up to, and if they didn't know they took time to find out. They invested the time in ensuring that Dad's naughty videos were under lock and key. They inconvenienced themselves to make sure that the shed had a locked cabinet containing the petrol and saws. No matter how much I kicked and screamed (and I was a 6'1" 15 year old in the school rugby team, I could kick pretty well), I wasn't allowed to go to the nearest major city unaccompanied until I was 16. When I did at the age of 15, I didn't see the outside for a month. Perhaps my parents were better at saying "no". But they did. And it worked.
And as for "the msn logs are the only source of finding out what the kids are up to these days", ever heard of Wireshark?