We paid extra for a digital box in our family room where I can lock out shows, shows by rating, channels, etc. But in other rooms we don't have digital boxes. Either my wife or I am always home to make sure that our kids aren't watching the other TVs unattended, but as they get older, this is going to be a concern.
And God help the millions of kids left unattended with this crap spewing into their homes.
All the TV's I've bought in the past couple of years have channel lockout built into the TV. Maybe it's time for a trip to Best Buy or something.