Nataraj Nagaratnam from IBM Cloud explains the shared responsibility model in cloud computing, emphasizing the different responsibilities between the cloud provider and the user in scenarios like Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS). He stresses the importance of understanding one's responsibility in managing security, compliance, and data when adopting cloud services. He also discusses the significance of designing a secure data architecture, including data encryption at rest and key management for better control and ownership of the data. Having control over keys and utilizing hardware security modules are highlighted as essential practices for ensuring data protection and maintaining control over sensitive information.