Citing FBI statistics, the report notes that violent crime increased for the first time in more than a decade in 2005 and in 2006. Homicides and robberies rose, while other violent crimes such as rape and aggravated assaults, along with all types of property crime, continued to trend downward.

"In this brief, we propose that the rise in violent offending and the explosion in the sales of iPods and other portable media devices is more than coincidental," the report says. "We propose that over the past two years, America may have experienced an iCrime wave."

The report goes on to characterize iPods as "criminogenic (creating crime)" because they lack antitheft protection, because they're not tied to a subscription service and can thus be used after they're stolen, because they're "high-status items and may be stolen for their status," because they make the owner less aware of his or her surroundings, and because they're easy to identify, thanks to the visible white headphone cord and ear buds.

While Apple declined to comment on the report, at least one patent filing, "Protecting electronic devices from extended unauthorized use," shows that Apple is researching ways to deter the theft of its products.

"Unfortunately, theft of more popular electronic devices such as the Apple iPod music-player has become a serious problem," the patent application states. "In a few reported cases, owners of the Apple iPod themselves have been seriously injured or even murdered. Hence, techniques that can protect against unauthorized use and deter and reduce theft of such devices would be highly useful."

That patent, a way to "brick" (render useless) an iPod or similar device by preventing it from being recharged, was filed Dec. 20, 2005.

The Urban Institute report concedes that "rigorous empirical tests of any hypothesis about the cause of the spike in violence are not possible." One problem is that Apple doesn't distinguishing between domestic and international iPod sales in its SEC filings. This makes it more difficult to correlate iPod sales in a given area and crime there.

In absence of hard facts, the report maintains that "anecdotal evidence is strong."

In the first three months of 2005, major felonies rose 18.3% on the New York City subway -- however, if cell phone and iPod thefts are excluded, felonies actually declined by 3%, thus prompting the Metropolitan Transit Authority to post warnings to riders that 'Earphones are a giveaway. Protect your device,'" the report says. "Thus far, in Washington, D.C., in 2007, robberies of iPods on the Metro alone account for approximately 4% of all robberies in the city, compared with well less than 1% of robberies in 2005. Likewise, in San Francisco's Bay Area Rapid Transit (BART) system, there were four reported iPod robberies in 2004, 102 in 2005, and 193 in 2006. The increase in iPod robberies on the BART between 2004 and 2006 accounts for a 23% of the increase in robbery in the entire city over that time."

In March, BART police warned riders to protect themselves and their iPods by being alert and by considering non-white ear phones.

A few months earlier, in December 2006, BART encouraged riders to carry iPods. "Carry your BART schedules right alongside your music!" the transit agency said in a press release. "Download the free, award-winning BART QuickPlanner for Apple iPod and you can look up train departure times, view a color version of the official BART system map and even check out general station information right on your Apple iPod."

The BART Police didn't immediately respond to a request for comment.

If there is an iCrime wave, it appears to be leveling off in San Francisco. "It's plateaued and dropped some since last year," said Lt. John Loftus in the robbery division of the San Francisco Police Department. "We see it trending down in 2007."

According to Loftus, there were 195 iPod robberies last year involving force or fear. This year, he said, the SFPD sees about seven iPod thefts per month on average. "They're not quite as hot as they used to be," he said. "However, they're still obviously a target."

Loftus added that iPods aren't the only hi-tech items targeted by thieves, noting that laptops thefts rose at a rate similar to iPods in the past.

The SFPD hasn't received too many reports of stolen iPhones, Loftus said. "Folks know that when they spend $600 on an iPhone, they had better be careful," he said.

The price, now $399, may not be the issue as much as the iPhone's informational tether to Apple and AT&T. In fact, the Urban Institute's report sees value in making information about devices more available to law enforcement. It concludes that "To prevent the next crime wave, policymakers must invest in real-time data systems to identify and respond to consumer-driven changes in crime."