There are plenty of open source blacklists out there that are far more reliable than the corporations, a lot of us already apply some kind of filtering anyway -

There are plenty of open source blacklists out there that are far more reliable than the corporations, a lot of us already apply some kind of filtering anyway - think AdBlocker. Of course, if you can educate your kid about the internet and feel that they are responsible enough not to need the software (maybe just keep the PC downstairs?) then that would be the better way to do it.