We wondered earlier, in reference to the Newburgh Four: is sending a government mole out to scrounge up a few dim-witted ex-cons who can be talked -- and perhaps bribed -- into getting involved in a fictitious bomb plot really the best way to use our limited terror-fighting resources?

The picture is still a long way from being clear, but a prominent counter-terrorism expert we spoke to confirms there are legitimate questions about the wisdom of the approach.

Vince Cannistraro, who served as the first operations chief of the CIA's counter-terrorism center, told TPMmuckraker it's doubtful that any of home-grown terror cases built through the extensive use of a government informant amounted to serious threats.

"There are some questions about whether or not these are serious attempts -- or are they organized by the FBI?" said Cannistraro, who now works as a private intelligence and security consultant. He cited the case earlier this decade in which the same government informant as in the Newburgh case helped convict two Albany, NY men for involvement in a scheme to launder money for a fictitious terror plot. "I don't think it was a serious threat," said Cannistraro, referring to the Albany case.

Cannistraro added: "If you had a real al Qaeda operation, you would never pick them up this way," but said that "the jury is out" on whether, on balance, the Feds' reliance on such tactics is a good thing or a bad thing.

Cannistraro also said that the tactic of using government informants to infiltrate mosques was losing whatever value it may ever have had, as worshipers become aware of the tactic. Indeed, many senior members of the Newburgh mosque appear to have correctly spotted the informant in this case as a government mole. "There certainly has become a widespread belief that Federal law enforcement uses the informant approach to instigate criminal activity" at mosques, said Cannistraro.

Not everyone agrees. James Carafano, a homeland security expert at the conservative Heritage Foundation, called these methods "the single most effective way to break up domestic terrorists."

Carafano, who served as an Army lieutenant colonel, and has written widely on military and homeland security topics, described the tactics used in the Newburgh case as standard. "Normally an informant is integral to the plot," said Carafano. "They offer something that the group really wants and can't get on their own. That is just very very common." He added: "We've been doing investigations of the kind of decades."

Still, as TPM's own David Kurtz points out, the evidence suggests that the FBI would have been most likely to sniff out 9/11 by putting more resources into running down the tips they were getting about suspicious behavior at flight schools, not by doing more to use informants to infiltrate mosques.