When it comes to cloud security challenges, which of these have been especially difficult to address so far? (You can choose all that apply)

Establishing a Cloud Governance Model which lays foundations for maintaining cloud assets inventory including governance of spinning new cloud accounts and subscriptions post establishing business use case, should have been a listed option/challenge in your question. Lacking single pane visibility of cloud assets assigned to your enterprise, is often the root cause of all the challenges you've mentioned above.