I think the precise answer is, there isn't one - really, a decision like that would come down to a willingness or otherwise to accept risk, to put measures in place that can be seen to (if not necessarily actually do so) mitigate that risk. I'm sure convincing arguments could be made which would support a range of decisions.
That's the quandary, a lot of decision making can't be quantised, it's subjective, so not everyone's going to be happy.