I had heard of a proposed legislation where porn sites would be required to use a new domain name, .xxx. I think that would be great because it would be much easier for parental controls to block porn sites. The porn sites would be segregated from normal sites.
The internet is for everyone of all ages though. That's why I think porn sites should be wiped off the internet or at least be segregated with .xxx domain name. No one under 18 should be staring at porn. For that matter, no one at all should be staring at porn.
As for letting your kids go at 13, I don't think so. 13 is not the age to give to them that kind of responsibility. 16 is when responsibility for themselves should start to really be kicked in with them.