I've mostly been on the "user" end of buggy internal company code. It's always a scary day when the interns start, because we finally have someone who will have the time to "fix" the bugs in the code--but half of them we have been using off-label as "features" to solve other problems.

Whenever I start at a new company, I make sure to ask not just what breaks the system, but how the system breaks when it breaks. One person's broken pot is another person's cutting tool!