Ashton Kutcher, the world's most popular Tweeter, on Twitter

Ashton Kutcher -- with almost three million followers, the world's most popular Twitter user -- says social-networking and other online collaboration has forever changed media.

"You can broadcast to millions of people, who can respond and influence that media," Kutcher said today at the Fortune Brainstorm Tech conference in Pasadena, California. One voice has as much, if not more influence, than the voice of a network, he said. And the change is permanent.