My kids (two young teenage boys) have access to my computer/s and I control what they can view by blocking inappropriate sites via the transparent proxy set up on my linux box/gateway. ACL's under squid take care of this.

I am not looking over their shoulders every minute of their time on the net but I do take responsibilty for what they can and can not do. I do take a quick look at the access log (kids are aware of this) on the proxy and if I find a site that is in my opinion is inappropriate it goes into the "blacklisted sites" - this included porn, warez, hate sites etc .... this also shows them that just about anything you do with a computer is recorded somewhere and can be looked at by someone.

If they feel they "need" to access a site I have blocked - they can come and talk to me and we look discuss why they "need" access. I have also blocked access to IRC for the kids but this can be opened and used under supervision if required.

This was very easy to set-up, difficult/impossible for them to by-pass (nobody gets the root password, not even the wife) and gives me piece of mind and time to get on with other things while they are on the net.

I am not a prude and I'm sure if they want to look at porn they are going to, but as a responsible parent I'm not going to make it easy for them to access or for others to push it in their faces.