In addition to Facebook's non-participation in Open Social -- in which MySpace and Yahoo are players -- Facebook starred in a public spat with Google this year when it blocked Google's own data portability system.

There are many privacy and security issues that need to be worked out as well before wide-ranging interoperability can be accomplished, and Facebook wants to make sure it doesn't compromise its members' ability to control their profile information, Zuckerberg said. "A lot of these problems will be solved over time, but I don't trivialize them," he said.

No matter what happens in the short term, Zuckerberg said he's confident that in the long run, both in Facebook and in the Web ecosystem in general, there will be a high degree of openness and interoperability among Web sites.

"As time goes on, we'll see this very natural fanning out and decentralization of things," he said.

Although early in his career he got a reputation for being cagey and circumspect in public appearances, Zuckerberg appeared much more candid and confident on stage, even when Battelle needled him with some questions.