If you have built layered architectures in the past, you can probably relate to some of the disadvantages discussed in this chapter, and you could maybe even add some more.
If done correctly, and if some additional rules are imposed on it, a layered architecture can be very maintainable and make changing or adding to the codebase a breeze.
However, the discussion shows that a layered architecture allows many things to go wrong. Without very strict self-discipline, it's prone to degrade and become less maintainable over time. And this self-discipline usually becomes a little less strict each time a manager draws a new deadline around the development team.
Keeping the traps of a layered architecture in mind will help us the next time we argue against taking a shortcut and for building a more maintainable solution instead – whether in a layered architecture or a different architecture style.