Builders and homeowners have long known how popular copper can be with thieves, but now the FBI does too.

Last week, the agency said that the problem of copper theft is endangering both public infrastructure and private property as criminals strip copper wire from electrical wiring at power stations, construction sites, foreclosed homes, water irrigation pipes, tornado sirens, and more. "Individually, these isolated crimes cause big enough headaches of their own," the FBI said in a written statement. "Taken together, however, they present a fairly significant problem for our country—a threat to public safety and to U.S. critical infrastructure."

The reason for such theft is, of course, money.

Wholesale prices for copper hit $8,900 per metric ton this summer, according to John Mothersole, principal with IHS Global Insight's pricing and purchasing service. "When prices reach those levels, scrap yards become more aggressive in their collections," he says, and less concerned about the, ahem, provenance of such metals.

The FBI did not provide an estimate of how much copper theft costs the country, but the U.S. consumes approximately 2 million metric tons of copper annually, according to Mothersole. Overall, nearly half of copper consumption goes for residential and commercial construction. The next biggest copper user is electrical power and equipment, which is responsible for 28% of copper consumption.

Today's economy, unfortunately, provides countless residential opportunities for illicit gathering of "scrap" copper from popular sources such as architectural details, water pipes, and electrical wiring. One group of thieves in Ohio actually used HUD listings of foreclosed homes to develop their list of targets, according to the FBI. Many are even more gutsy—or foolhardy. "This summer people were ripping out transformers to get at the coils. Live [electrical lines] were being pulled out," Mothersole says. "People were getting electrocuted."

But the rationale behind such risky (and criminal) behavior is disappearing.

Copper theft "has been a problem, but it won't be much of a problem any longer," Mothersole predicts. "Copper prices have just collapsed," falling by two-thirds to $3,300 per metric ton on the wholesale market in December. "It's just not worth the trouble now" to steal copper, he says.

The reason, of course, is the economic malaise. "Granted, copper prices were at elevated levels [this summer, when the metal sold for $8,900 per metric ton wholesale] but the turn has just been incredible," Mothersole says. "It speaks to how fast the general economy has deteriorated."

Alison Rice is senior editor, online, at BUILDER magazine.