I learned at Slashdot of an article at Financial Times about criminals extorting companies by subjecting them to denial of service attacks. From the article:
"More than a dozen offshore gambling sites serving the US market were hit by the so-called Distributed Denial of Service attacks and extortion demands in September and the tactic is now spreading. Sites have been asked to pay up to $50,000 to ensure they are free from attacks for a year. Police are urging any victims not to give in to blackmail and report the crime."
This is a lot easier than breaking into a victim and extorting them for theft of credit cards or intellectual property. Just have your home users and university machines blast away at a victim and collect the cash.