eDiscovery and Audit Logs
One of the tools he mentions is the Audit log, and I agree. It can be difficult in SharePoint and OneDrive to determine who saw a document and who didn’t, because there are often so many changes being made at once. It’s easy to get lost in an avalanche of versions and permissions that leave doubt as to whether something was even shared with a user during the time in question.
That’s where the audit log comes in. However, just because events are logged doesn’t mean they will still be there months from now. If you’re in a highly litigious industry, the retention and preservation of audit log data might be something worth considering.