Vaginal delivery vs. C-section

I am really hoping for a vaginal delivery, but understand that a c-section is a possibility in an emergency. I keep hearing that my Dr. is c-section happy, in fact a friend of mine who has the same Dr. just had a baby via c-section, that wasn't 100% necessary. She learned later that in her chart it read "the patient opted for a c-section" after learning she had placenta previa (that wasn't significant enough to require a c-section) though she said she was never given the option. My understanding is that a Dr. must provide evidence that a c-section is necessary, but I'm unsure of what the regulations or criteria are. Anyone have any information or have any experience with this type of situation? Thanks!