Who is ultimately responsible for a data breach that includes personally identifiable information (PII), in the event of negligence on the part of the cloud provider?

The "user" is a broad term, often referring to an end-user of the customer's services, and does not hold ultimate responsibility for organizational data breaches.

The "subject" refers to the individual whose PII was breached; they are the victim, not the responsible party.

While the cloud provider may be contractually liable for their negligence and may face fines or legal action, the ultimate responsibility for data ownership and regulatory compliance often rests with the cloud customer.

Under the shared responsibility model, the cloud customer typically owns the data and is ultimately responsible for its governance, compliance, and overall protection. Therefore, they retain ultimate accountability for data breaches, especially concerning Personally Identifiable Information (PII), even if the cloud provider is negligent.