Twitter's Evan Williams Tight-Lipped About Rev Model, Notes U.S. Traffic Has Slowed

twitter-bird1Twitter’s U.S. traffic to its main site has slowed, CEO Evan Williams said during a talk at the Web 2.0 Summit in San Francisco this afternoon, but said that the company was launching new things that “will pick that back up.”

It’s still unclear how the micromessaging site intends to make money, however. “It’s not like we’re spending our days looking in the couch cushions for our revenue model,” said Williams. “You wouldn’t raise that much money unless you have something plausible.” This was a clear reference to the company receiving $100 million funding last month that valued it at a whopping $1 billion.

Reports surfaced earlier this month that Twitter was in advanced talks with Microsoft (s msft) and Google (s goog) to serve real-time tweets in their search engines. But Williams was coy when asked onstage about these rumored search deals, quipping, “Whose deals?”

Right now, Twitter is toying with the idea of putting ads on its site, though co-founder Biz Stone said it doesn’t plan to do so this year. But last week, Twitter launched a mobile version of its service in Japan that will incorporate money-making features such as banner ads. This mobile version will be a testing ground for the company and will help determine whether it will ultimately incorporate advertising on its site. Twitter has also made clear that it will offer enterprise services for businesses, including analytics and verified accounts. Earlier this summer, the upstart made a step in that direction by rolling out its Twitter 101 web-based guide aimed at helping companies understand its service.