Well... no matter who the manufacturer is, there is always a possibility of having hidden problem. I think the argument is, when problem occurs, whether the manufacturer will take the responsibility to correct it ASAP. There is no way to guarantee 100% that a car does not have any potential problem. When they say it's "safe" to drive, it means the probability of having mechanical problem is very low.
I hope Toyota's case is a good lesson to everyone, so we'll be able to enjoy driving better. After all, we're the users.