This article from Wired reviews 10 of the worst cybercrimes between 2000 and 2010.
It is noteworthy that 3 of the 10 crimes targeted random unpatched/unprotected computers for use in bot armies. The others were fraud and money scams orchestrated by international networks of thieves.
Two lessons to take from these attacks, keep your computer up to date, keep track of your credit and credit card purchases. Make sure to report any suspicious activity quickly to your credit card companies.