I've seen a lot of enterprise-y programs that do this and it just looks lazy. The poor user enters some invalid input data and the program crashes, and the deve

I've seen a lot of enterprise-y programs that do this and it just looks lazy. The poor user enters some invalid input data and the program crashes, and the developer points at the spec and says "there was nothing in here about validating and giving an helpful error message". The assumption seems to be that "ad-hoc decisions" made by the programmer, are often worse than crashing. I'm not sure that is often true. Who is supposed to be the domain expert, the person writing the spec, or the developer? Perhaps asking the spec-writer what should happen in the situation would be better than just letting it crash. There is a business cost to crashing, and businesses are normally the ones paying for the software.