From Mark Everett Hall at ComputerWorld: Cloud computing safer than on-premises:
For a cloud computing provider, the business is IT. For most companies, IT serves the business. As a result, a cloud computing operation's primary business investments will be in the computing infrastructure and staff. In most organizations, IT competes for limited resources and people.
I definitely agree. What makes the data important is not that it is behind a firewall and that employees are trying to keep it inside. Some things that are important is whether processes are in place to constantly update systems with patches, that systems are constantly monitored for irregularities and that people in charge of these systems are very very good at what they do.