Security is not compatible with business. The government says that classified information is not on computers that are connected to the Net. It's usually not. But you'd be surprised how many modems are still available to dial into. Last fall, hackers broke into Microsoft's corporate network and accessed source code for the latest versions of Windows and Office.
Big companies tend to have more sophisticated processes and better source-code control.
Hacks there are more likely to get noticed. But small companies tend to be more careless. Which is why it would be the perfect target. Between mIRC, Napster, Eudora, and Winamp, you probably have about 85 percent of the Windows computers on the Net. That requires skills most hackers don't have.