An excellent question was asked in a different thread: How many of these random internet threats are there a day, and what makes this one special?
http://sportsillustrated.cnn.com/2006/football/nfl/10/18/stadium.threats.ap/index.html?cnn=yesWASHINGTON (AP) -- A Web site is claiming that seven National Football League gridiron stadiums will be attacked with radiological dirty bombs this weekend, but the U.S. government on Wednesday expressed doubts about the threat.
The threat, posted Oct. 12, was part of an ongoing Internet conversation titled "New Attack on America Be Afraid." It mentioned NFL stadiums in New York, Miami, Atlanta, Seattle, Houston, Oakland and Cleveland, where games are scheduled to be held this weekend.
The Homeland Security Department alerted authorities and stadium owners in those cities, as well as the NFL, of the Web message but said the threat was being viewed "with strong skepticism." Homeland Security spokesman Russ Knocke said there was no intelligence that indicated such an attack was imminent, and that the alert was "out of an abundance of caution."
The FBI also expressed doubt about the threat.