Interesting read: http://www.nationaljournal.com/njmagazine/cs_20080531_6948.php

Some interesting parts:

A second information-security expert independently corroborated Bennett’s account of the Florida blackout. According to this individual, who cited sources with direct knowledge of the investigation, a Chinese PLA hacker attempting to map Florida Power & Light’s computer infrastructure apparently made a mistake. “The hacker was probably supposed to be mapping the system for his bosses and just got carried away and had a ‘what happens if I pull on this’ moment.” The hacker triggered a cascade effect, shutting down large portions of the Florida power grid, the security expert said. “I suspect, as the system went down, the PLA hacker said something like, ‘Oops, my bad,’ in Chinese.”

 and this part:

Bennett, the former head of the Cyber Security Industry Alliance, said that if China has penetrated power plants and the power grid, it serves as a show of force to the United States and is likely meant to deter any U.S. military intervention on behalf of Taiwan. He noted that the Florida blackout occurred only a few days after the Navy shot down a failing U.S. satellite with a missile designed to intercept inbound ballistic missiles. A year earlier, the Chinese had downed one of their own satellites in orbit. The Bush administration has pursued ballistic missile defense systems, and Taiwan has sought that technology from the United States.