Facebook's ad business is humming along nicely, generating a healthy cash stream both from direct sales to big brand marketers and from smaller advertisers that buy space on the site using its self-service tools, Zuckerberg said at the Web 2.0 Summit in San Francisco.

Generating "hundreds of millions of dollars" in annual revenue has allowed the company to focus on growing its worldwide user base this year to about 125 million members and to not have to make revenue generation its top priority, he said.

Industry pundits have suggested recently that, given its fast growth, Facebook may be approaching a cash crunch that could affect its operations and force it to seek more funding, but Zuckerberg dispelled those ideas.

Likewise, the staggering $15 billion valuation doesn't weigh around the necks of staff, nor does it dictate the company's business strategy, according to Zuckerberg. "We don't feel any pressure to live up to the valuation," he said.

By the same token, Microsoft's $240 million investment is just one piece of the companies' collaboration, which also includes partnerships for online ads and search technology, so Zuckerberg isn't worried about Steve Ballmer regretting what he paid for the Facebook stake. "They have been a really good partner for us," he said.