I don't think that this would be a good thing

I hate censorship of any kind. A decision like that would devastate the porn industry. I think that if the US wants to keep kids off of porn, then they should develop one of the highest quality adult content blocking software programs ever made and give it out as a free download. If parents want it, they can download it and pop it on OR perhaps maybe ole Bill Gates can somehow incorporate it into IE.
For all of you that are thinking about the SE source of traffic. My prediction on that matter would be that all of the big SEs like Google would see a big potential to charge sites to be listed in their directories, thus, fucking a lot of the smaller guys OR on the other side of it, would they even be able to legally list adult sites without having the surfer verify their age first ???