Parents have become very aware of the safety issues, maybe through the negative (publicity) this industry has received.
Parents get feelings about nannies and you need to trust that. They are very accurate. If you feel like something is not right, or you've got a bad feeling about what is going on in your home while you are away at work, you are probably right. Act on that immediately.
In the last five years, demand has been so great that there is actually a nanny shortage. Parents are waiting in line for them.