I think this a very realistic and worrying possibility. I can easily imagine a scenario:
Workday runs Payroll for hundreds of customers in a single environment. Each company has its own "tenant," but all the data is stored, together, in Workday's one big in-memory database. Workday is entirely responsible for backups, disaster recovery, etc.
Assume your company uses Workday for payroll services. Now imagine that some other company that is also using Workday is using fake employees in the Payroll system to launder money. We all know "money laundering" is all the FBI really cares about, so they eventually figure out this is happening. What is keeping the FBI from shutting down Workday, entirely? If they do shut Workday down, I'll bet your company will be destroyed by the fact it can't pay it's employees, and by the penalties the IRS will impose when you can't file your taxes.