Bill Nguyen's not the kind of guy you'd peg for self-loathing. The serial entrepreneur is like a brilliant four-year-old on a sugar high: perpetually on the edge of his seat and not above bouncing up and down when someone else has been talking for more than 10 seconds. If that's not a good enough description, let's just leave it at this: He's a huge fan of Jersey feelgood band Fountains of Wayne. (Anyone out there remember Stacy's Mom?)

Which is why it was so surprising to hear Nguyen reflect on his personal history and the state of innovation in the Valley. Nguyen came by my San Francisco office yesterday to talk about his latest startup, the CD-sharing site LaLa. Part Netflix, part Web 2.0, part used record store, LaLa has been on a tear. Two hundred thousand users have offered up more than 5 million CDs for trade at a cost of $1 each plus 75 cents handling. It's one more example of the rash of brilliant discovery sites cropping up on the Web lately and Nguyen is obviously excited about the idea. But it's not the best idea he's had. That honor, he says, would have to go to his first startup, unified messaging company Onebox, which he sold for $850 million in 2000. "Here's what I think about the whole serial entrepreneur thing: Every time I do something, I suck a little bit more," Nguyen says. "Experience teaches you to be less bold, more concerned. All these life experiences teach you to be afraid. I have to try so much harder now not to be the sum total of my experiences."

Nguyen overcomes his own tendency to think about droll topics like business models and return on investment by surrounding himself with naive twentysomethings. "We hire a bunch of young kids and let them do whatever the hell they want." Needless to say, Nguyen is baffled by the tendency of venture capitalists to seek out second and third-time entrepreneurs, thinking that they're less likely to repeat mistakes. (LaLa has raised $9 million from Bain Capital.)

As we were talking, I thought about a piece I edited at Wired by Dan Pink about a University of Chicago economist who has devised a universal theory of creativity. In a nutshell, the economist claims there are two kinds of innovators: conceptualists and the experimentalists. Conceptualists make their mark early in life and never reach that peak again (think: F. Scott Fitzgerald, Orson Welles, Bill Gates?). Experimentalists toil away their entire careers and peak much later in life (Mark Twain, Alfred Hitchcock, Steve Jobs?). Nguyen, who studied economics, doesn't see it that way. He thinks world-changing companies just don't come from the minds of thirty and fortysomethings. But I think he's being hard on himself -- and his peers. I think experience has a lot going for it -- and as long as that wisened thirtysomething knows enough to hire a bunch of brash kids, the combination can be pretty incredible. But maybe that's just because I'm fast-leaving my mid-thirties.

What do you think? Should Silicon Valley have an age limit? Do second-time entrepreneurs suck?