My son for example is 6 - and very inquisitive - for that reason he is already restricted when he goes online.
But given how widespread advertising is for ISPs (Billboards, Magazines, Radio, TV, etc, etc) my son knows a lot about ISPs (even if he doesn't know the term itself)
He doesn't yet know about a VPN but he knows about the internet and wireless and windows, etc purely by being around us and through his own initiative he has learnt about stuff we haven't told him - We've found him on sites like Argos and Smyths and with toys added to the shopping basket!
Children soak in information like a sponge - hell he can find his way round Windows 8 better than I can!
The Little Johnny scenario is not that far from the truth..
it comes back to Education - the more we educate our children about the dangers the more they will be aware of them.
Children choke on food - we don't ban them - we educate the child on how to eat it safely
Children get knocked down - we don't ban cars or buses - we educate them on how to cross safely at crossings.
Children can drown in a paddling pool - do we ban them? no we don't - again we EDUCATE the child and we supervise the child whilst they are playing.
Children can get kidnapped - bugger all we can do about banning other people - we EDUCATE them on not talking to strangers, on what do do/say if someone tries to take them (We say to scream very loudly, make a lot of noise and if possible find a policeman)
Ergo, we should be doing the same with Pr0n - we should be deciding whether to have a filter on or not, we should be educating our children on the dangers of what they see online, on how to be safe - we should be watching what they are up to..
Complacency is a very dangerous thing...