It would be highly contradictory for MS to take the position, as a matter of policy, that it is too risky for them to ever place confidential business data onto a third party cloud-hosted SaaS system, because that is precisely the risk they are asking every one of their customers to take.
Similarly, if you have concerns about putting your company's source code into GitHub now, you should be equally concerned about putting your company's prerelease annual report on the office365 onedrive.
That is a good point though, it’s becoming more and more inconvenient for a company to self host everything. Microsoft does stand to benefit from everyone becoming more accustomed to relying on 3rd party services in the cloud.
Essentially, choose your vulnerability: cloud provider single point of failure or in-house lack of resources