Yet another data point:
Doctors Behaving Badly: FDA says UCLA cardiology chief botched clinical trial
In this case, the billing-for-services-not-actually-provided is obvious. The UCLA cardiology chief in question was paid to monitor the health of his patients, ensure their rights were protected, ensure that record keeping sufficient to maintain the usefulness of study results was done, and more. Allegedly, none of those things were done.
The omerta part is pretty obvious too. One patient died, and one underwent multiple hospitalizations while in a clinical study -- and no one told the institutional review board nor the study sponsor for a year. The study continued during that time.
As at the top of this post: just another data point.