A sad example is provided by Texas. Protection against bad doctors was provided in Texas by three things: the Texas Medical Board, malpractice suits, and hospital managers. The legislature greatly limited the amount patients can win in malpractice suits, and they made it so hospitals cannot be held liable for hiring incompetent doctors unless the plaintiff can prove the hospital knew the doctor was an extreme risk and ignored this--and they made it so the plaintiff usually cannot get access to the documents that would be needed to prove this.
This shifted most of the burden of protecting Texans from bad doctors to the Texas Medical Board, which was not designed for that. It was more designed for licensing and ensuring that doctors keep with standards, not for investigating bad doctors. The Medical Board was not given any more resources to deal with this new and heavy workload, and so bad doctors could practice much longer than they would have been able to before the legislature decided to do their tort reform.
This article on the Dr. Christopher Duntsch case shows who wrong this can go: http://www.texasobserver.org/anatomy-tragedy/