A CSO-US Secret Service-Carnegie Mellon survey concludes that over 83% of businesses experienced losses due to computer crimes. Surely you knew that, of the top five, email is often the preferred delivery method.

Electronic Crime %
Virus or other malicious code 77%
Denial of Service attack 44%
Illegal spam messages 38%
Unauthorized access by insider 36%
Phishing 31%

See for yourself at 2004 E-Crime Watch Survey.