Ideally you want both, this is just one of many types of structures used to reduce the likelihood of such events happening. As for why we have any id at all, th

Ideally you want both, this is just one of many types of structures used to reduce the likelihood of such events happening. As for why we have any id at all, there is a degree of risk vs reward that has to be traded off, and this current point along the equilibrium has worked well so far.