It has been known for years that doctors cover each others' butts. I think that the attitude comes out of a time when a doctor's advice went unquestioned. There is also the spectre of malpractice, which has gotten completely out of hand. Apparently, unless a doctor's behavior is totally egregious, it is not reported.
Personally, I could cite a number of instances in my own life, and the life of close family members, where doctor error has caused negative ramifications. Were I of a more litigious nature, I probably would have had good cause for initiating a number of lawsuits.
I recently had a procedure at a facility where the doctor had a financial interest. To his credit, before I actually had the procedure, I had to sign a paper that I understood the doctor's commercial tie to the facility. I had once been to another surgery center, where it was whispered that the doctors owned the facility, but I was never told upfront about the relationship.
As far as treating poor patients, IMO, people are not entitled to medical service just "because". Medicine is a means of making living for a doctor, and I don't believe that he is obliged to service all comers, whether they can pay or not. I think that it is admirable when a physician apportions a part of his practice to serve the poor, but I do not believe that it is obligatory. It is fashionable though, for a doctor to SAY that he believes in serving the poor.