Fortune magazine's Brainstorm: TECH summit in Pasadena, Calif., got Punk'd, as actor Ashton Kutcher spoke with Fortune managing editor Andy Serwer about Twitter.

On why he uses Twitter:

One, I find it fun. I find it entertaining. Two, I think it gives you an ability to stay in tune with your audience and trends, what people are finding interesting. But also, it gives me a great platform to syndicate content on. I mean, companies that make a $50 million movie, they spend $10 million-$20 million to market it, trying to reach an "Ashton Kutcher audience" to go see the new movie I'm in…I can do it with the push of a button. For free.

On why he thinks Twitter is so successful:

By the way, it's not going to be the last one…someone is going to come along and usurp it. Twitter is just the first micro-blogging institution. Eventually, someone is going to come along…and do it in a way that the search is more relevant, that you can re-syndicate easier…But the real value of it currently is that it's alive…You can sit in front of your computer and watch a living thing take place…That's the closest thing that the Internet has come to television thus far.

On his Twitter following:

I don't have 3 million followers because I'm a really good poster. I have them because I'm famous. Right now, most of the people who are stars on the Web are really cheap resources—like (IAC chairman and CEO Barry Diller) said this morning, they're making movies for $5,000, $6,000, $7,000. Unless movie stars can leverage the platforms to keep themselves relevant, they are going to become less and less relevant…I think it's really a survival tactic.