From the 2nd page of the article:
What happens now? Two words: Privacy scare. Security and privacy advocates are already poring over Zuckerberg's words to find ways that the as-yet-unseen mail system might compromise its users. But from past experience, security holes are unlikely to slow the Facebook juggernaut. "The only fatal shortcoming would be a very serious breach of privacy that would scare anyone from using it," Bernardo Huberman, director of Hewlett-Packard's Social Computing Lab recently told Technology Review. So far, though, it seems Facebook users mostly choose to complain bitterly about Zuckerberg's privacy goofs while using his site nonstop.