It's why, in this agile world, I prefer noobs to use cases to user stories. Most templates I found explicitly prompt you to think about fail conditions. If you're wondering what constitutes being a noob, it's when someone is too inexperienced to think about fail conditions and work them through without being prompted by someone or something, like your app crashing out.

Note that I have nothing against inexperience - I used to be too. And noobs are malleable - in that sense they're easier to work with than experienced people.