Who is responsible for a compromised computer?

In light of the recent public hacks on public systems, is there any culpability for the owner of a compromised system? Two examples:

1. The owner is a large public company that leaks sensitive information through a malicious hack (for arguments sake, assume it came from the outside).


2. Your personal computer unknowingly participates in a DOS attack through a botnet.

Both of these carry legal penalties if they were committed knowingly. To make this question concrete and not subjective, "is there legal precedent in the US, either for or against, concerning the culpability for the owner of a hacked computer?".