This sort of thing is not unique. Two years ago the FBI arrested a 22 year old navy intelligence specialist, who was offering to sell American secrets long term to the highest bidder. The young spy was caught by the FBI, who detected his efforts and approached him in the guise of a foreign government to do business. The sailor delivered and was arrested.
Throughout the Cold War the Russians found that greed was the best way to get Americans to betray their country. That's only one of the five reasons for spying. The others are ideology (there were never enough American communists to supply the Russians needs), conscience (people who spy because they believe their government is wrong), compromise (the Russians often used sex, the Honey Trap, to ensnare Americans and coerce them to spy), and ego (people who get off on doing something dangerous, like treason).
One of the most valuable American spies the Russians ever recruited was basically an FBI agent with ego issues. Eleven years ago the FBI arrested one of its veteran counterintelligence agents, Robert Hanssen, for espionage. Hanssen worked for Russia from 1985 until 2001, earning $1.4 million in the process. For the Russians, Hanssen was the perfect spy. He was the much feared, and long suspected, Russian mole in the American intelligence establishment. Hanssen didn't do it just for the money. That was just how he kept score.
Hanssen had something of a Walter Mitty complex, seeing himself as a dashing secret agent. Since he was a senior agent working in counterintelligence, he was in a position to know who the FBI was currently looking for and how best to avoid getting caught. But he didn't have access to a top secret FBI/CIA "Mole Hunting Squad," which eventually arrested him. The FBI, much to Hanssen's distress, had a perfect spy of its own.
Hanssen was a dour and colorless agent. He was one of the FBI's first computer experts. He was quite the professional's professional. For example, he never let the Russians know who he was. The Russians didn't care, as Hanssen provided quality information, which sabotaged dozens of (sometimes very expensive) U.S. spying operations. Hanssen's work also got two U.S. agents in Russia (KGB officers) executed. This last item caused the FBI to call for Hanssen to be executed. That was possible because, after Aldrich Ames was caught in 1993, and it was revealed that his work resulted in ten U.S. agents being executed, the law was changed to make spying that got foreigners working for the U.S. killed a death-sentence offense. Hanssen avoided execution only by pleading guilty. He is currently serving a life sentence, spending 23 hours a day isolated in his cell.
The damage Hanssen did was considerable, and Hanssen beat the death penalty by speaking freely about what he gave the Russians. Knowing what the Russians know about our spies, and attempts to catch spies (counterintelligence), makes it much easier (although still quite expensive) to repair the damage. Many current American spies were compromised, being watched by the Russians and fed false information. Hanssen's reports to the Russians have made it much more difficult to catch Russian spies. Moreover, since the Cold War ended, Russian espionage has concentrated more on economic targets. Many of their spies are now looking for secret information on new technology and trade negotiations. Post-Cold War espionage has been more about making money than winning wars.
In one respect, Hanssen was quite unusual. After the Soviet Union fell, and Russian spymasters could talk somewhat more freely, they admitted that the easiest way to recruit American spies was with money. Hanssen was attracted mainly by the adventure of it all and apparently spent very little of the money. He admitted as much in his letters to the Russians and stashed the cash in an offshore bank. He was thinking of leaving it to his six kids, long after he retired from the FBI and was less likely to be watched.
In other parts of the world, the Russians could use their preferred (and cheaper) method for recruiting: ideology. But the supply of dedicated communists was drying up in the decade before the Soviet Union fell and the recruiting worldwide was more frequently done with cash.
The Russians also had an advantage in that they did not have any moral scruples, and no pesky Congress or public opinion to crimp their style. The Russians needed these advantages, for although they were able to attract the best and brightest recruits within Russia, the KGB itself was a petty, bureaucratic, and paranoid organization. These were not particularly bad traits for an espionage organization that depended so much on spies (or HUMINT - human intelligence operatives). The Russians were always carefully monitoring the loyalty of their own agents. America's greater dependence on "technical means" (satellites and electronic eavesdropping) kept the United States well informed about what Russian military capabilities were.
Another result of the Soviet Union's disintegration was that Russians were even more tempted by cash. Many of their brightest agents left for more profitable civilian opportunities. For the same reason the best recruits were no longer available. This made it easier for America to recruit Russians and buy information. Numerous long-time Russian spies have thus been compromised by America's buying secrets from former or current Russian intelligence officers. America recruited well-placed Russian agents, who provided information that led to the arrest of Hanssen. In fact, the entire file on Russia's most valuable American spy was delivered to the FBI. Having someone like Hanssen is a considerable advantage until your enemy gets someone of equal capabilities.