Airtime, a Pedigreed Start-Up, Is Tested

It sounds like a recipe for success for a new start-up: Two famed entrepreneurs, tens of millions of dollars in the bank and endorsements from celebrities like Alicia Keys and Jim Carrey.

But Airtime, the much-hyped video chat site created by Sean Parker and Shawn Fanning, the two behind the music sharing service Napster, has turned out to be far from a sure thing.

The site is just four months old, and the staff is tweaking its features to make it more appealing. So far, though, Airtime’s traffic appears to be little more than a trickle.

And the latest bits of news about the company — it has lost some important employees and laid off others — do not bode well for its future.