Alarming expectations have been rather strong in America after 9/11
The struggle with terrorism has failed. CIA and FBI experts have recently stated that new acts of terrorism are possible to take place in the United States within a month or two. Furthermore, American special services know who is going to organize them - al-Qaida, of course. Probably, one should treat such conclusions seriously, especially after the recent series of terrorist acts in the Middle East. However, this brings up a question, whether a threat of terrorist acts is good for the American administration (it goes about a threat here, not acts of terrorism).
Newsweek magazine reported that American secret services had managed to intercept several telephone conversations, the contents of which allowed to suppose that Osama bin Laden's terrorist network was preparing acts of terrorism in the USA. An anonymous American agent told the magazine that something like that had happened before the terror attack on America in September of 2001. Secret services did not pay much attention to those facts at that time, and the price of that was immense. It goes without saying that now the CIA and FBI administrations do not have a desire to make the same mistake again. That is why, they started talking about a coming terrorist attack.
On the other hand, one has to take account of other obvious things too. Alarming expectations have been rather strong in America after 9/11. The threat of more terrorist acts has already become a common thing to mention. However, the information about possible terrorist acts has not been always true. At the end of the day, it is good for the American administration to keep the tense situation in the country. This makes it a lot easier to justify the need of unpopular measures both in the States and abroad. One may give up certain democratic values and principles when it comes to the struggle with the international terrorism.
The other side of the story is more transparent, though. It is not excluded that American special services try to obtain more funds from the government in this way. This is a good tactics, for no one will venture to refuse funding the CIA, for example, if terrorists threaten the whole nation.
For the time being, the USA holds TOPOF-2 exercises to repulse terrorist attacks (Top Officials). Security Secretary Tom Ridge, whose department was created to prevent and deal with any future attacks, said the exercise scenario reflected plausible threats to the country.