This Is How You Catch Terrorists -- Not By Peering In Granny's Diaper At The Airport
It's targeted intelligence, based on probable cause, executed by highly trained intelligence officers -- people who might be anthropologists, lawyers or own their own business if they weren't working for the FBI. From WRIC.com, Betsy Blaney writes for the AP of a Saudi man accused of gathering materials to make a bomb:

During the first day of testimony in the trial of Khalid Ali-M Aldawsari, Special Agent Aaron Covey walked jurors through the 22-year-old former chemical engineering student's apartment in West Texas using photos taken hours after Aldawsari's Feb. 23, 2011, arrest. Prosecutors contend Aldawsari gathered bomb components with the goal of targeting sites across the U.S.

Prosecutors presented more than 80 exhibits Friday, many of them photos that gave jurors a first look at Aldawsari's sparsely furnished apartment near Texas Tech University. In addition to the bottles of sulfuric and nitric acids, prosecutors showed photos of cellphones, Christmas lights, journals and notebooks, a laptop computer, wiring, a stun gun, a hazmat suit and a baby scale.

Aldawsari faces up to life in prison and a $250,000 fine if convicted of attempted use of a weapon of mass destruction. Investigators say the targets he researched included the Dallas home of former President George W. Bush, dams and nuclear plants.

...Authorities say they were tipped to Aldawsari's online purchases by chemical company Carolina Biological Supply of Burlington, N.C., and shipping company Con-way Freight on Feb. 1, 2011. The chemical company reported a $435 suspicious purchase to the FBI, while the shipping company notified Lubbock police and the FBI because it appeared the order wasn't intended for commercial use.

...Court documents say Aldawsari wrote in Arabic in his journal that he had been planning a terror attack in the U.S. even before he came to the country on a scholarship, and that it was "time for jihad," or holy war. He bemoaned the plight of Muslims and said he was influenced by Osama bin Laden's speeches.

FBI bomb experts have said they believe Aldawsari had sufficient components to produce almost 15 pounds of explosive - about the same amount used per bomb in the London subway attacks that killed scores of people in July 2005.