In an earlier post I discussed the problems with Malware and the financial motivations for creating evil software. I mentioned that skilled Malware writers are no longer focused on pure mass propagation, but rather it has become a way to earn a living.
Kasperky Labs has published an excellent paper entitled The Economics of Botnets that puts some real world dollar values behind the motivations. The paper talks about just how easy it is to setup and manage a Botnet, as well as the insane amounts of money that can be earned. Well worth a read.