Every time a consumer purchases something like an automobile or other, similar product of industrial production, they are implicitly taking the manufacturer at their word that the product is safe to use and will not harm the consumer. This is the responsibility that corporations assume when they produce consumer goods, and if they can't live up to it, then they have no business selling goods to consumers at all.
Yes, GM waited too long to notify safety investigators of ignition switch problems tied to at least 30 deaths. GM should have notified the safety board as soon as a problem was identified. There is no excuse to wait, as it could (and did) lead to the loss of life.
GM knew before much of the public and their own customers that the ignition switch was faulty. The ignition switch would shut off at random times, even while the car was running and driving. This caused the airbags to be disabled and therefore would not activate during crashes, many of which were caused by the unexpected shutdown of the vehicle.
GM is a reputable company and has a higher standard quality service that consumers have expected from the car maker. It's important that GM holds those standards and so when information was delayed about the ignition switch, people became suspicious of the companies intent. The stock suffered and eventhough sales are at an all time, if they were more transparent, sales would have been extraordinary. Consumers have come to understand that not everything is perfect, but when a company disregards your trust, consumers will lash out.