Undocumented code can however keep you in a job! ;)
Programmers and car repairshops could share some similairities; they both "repair" just enough so the owner have to combe back very soon for a "checkup". I've spent enogh on cars to have decided to buy a new car.
I'd say watch out for 2 type of people in life: the software develeopers and car mechanics ;).