Most recently my sister had to hear that avoidable taxes will likely cost her the entirety of an inheritance from my mother that she was counting on for retirement (she is 60, has no other assets, little SS, no pension or health care and very little way of generating new income).
Due to this poor planning, in addition to over the top penalties for what most in most cases a paperwork foot fault, they are now often subjected to cost and stress that was entirely avoidable.