There are lots of hazardous substances that can cause lots of damage to lots of people. Dirty bombs are scarier, but probably wouldn't cause more real-life damage than a chemical attack (c.f. the Tokyo subway [link|http://en.wikipedia.org/wiki/Sarin_gas_attack_on_the_Tokyo_subway|attack]). How can I say such a thing? Well, consider [link|http://www.cdi.org/terrorism/dirty-bomb.cfm|this] article by the CDI; though as a counterpoint one should also consider [link|http://www.fas.org/faspir/2002/v55n2/dirtybomb.htm|this] one by the FAS.
My concern isn't the snooping so much - I agree that non-invasive searches are better for sweeping large areas than, say, mandatory door-to-door searches. My concern is that no warrant was requested. At some point, IMO, if you're on my land then you should need my permission to conduct sampling of my property. If you don't have my permission, then you should be forced to demonstrate to a judge that you need to be legally permitted to do the sampling.
I worry about the precedent this sets. If this is permitted, why not have the FBI drive up and down our streets with supercomputers and \ufffdbersensitive microphones and pentabyte disk-arrays, recording every sound for subsequent analysis and indefinite storage. Well, it's out there in public, so it's fair game - right? It looks like Bobby Jones down the street is a member of the NRA and likes to play FPS games - our software profiling indicates he might be training to be an extremist. Maybe we should have a record of what he does at home for the next 10 years - just in case...
:-(
I'm sorry - I don't buy it.
Radioactive materials don't grow on trees. Sources of large enough quantities of radioactive materials to be useful in a bomb are well know and are (or should be!) carefully controlled. (E.g Al-qaeda isn't going to go to Home Depot and buy 100,000 smoke alarms to make their bomb.) The transportation infrastructure could be monitored to see if radioactive materials are moving through it. Etc. Obviously, contacts with known extremists and terrorist groups should be carefully monitored (within the law). If law enforcement has some probable cause, or some legitimate reason to investigate a building or an area, then let them get a warrant. If they want a "clean baseline" to be able to quickly spot changes in an area, then that may be fine too. But unless there was more reason to investigate the mosques and homes of Muslims than was presented in the USN&WR report (and I didn't notice much of any), then they should have been forced to get a warrant to do the sampling on private property.
As you point out, recent court decisions may have reduced the need for law enforcement to get such warrants. If so, I think that's a bad trend.
Bottom line: A court should act as a civil protection to prevent directed fishing expeditions that don't meet a reasonable standard of necessity or probable cause.
My $0.02.
Cheers,
Scott.