From the New York Times, Silicon Valley Start-Ups Awash in Dollars, Again:
Twitter, a company in San Francisco that lets users alert friends to what they are doing at any given moment over their mobile phones, recently raised an undisclosed amount of financing. Its co-founder and creative director, Biz Stone, says that the company was not currently focused on making money and that no one in the company was even working on how to do so.
“At the moment, we’re focused on growing our network and our user experience,” he said. “When you have a lot of traffic, there’s always a clear business model.”
Translation: we lose money on each customer, but we make it up on the volume.