> What's actually wrong with it though? Why isn't it still "good enough"? Anyone who has had to try to manage security permissions on a big flat list of files

> What's actually wrong with it though? Why isn't it still "good enough"? Anyone who has had to try to manage security permissions on a big flat list of files knows it's like holding jello with rubber bands. As an another example people might be familiar with: having to manage a big PHP or Ruby codebase where everything is separated by the models, views, and controllers a hierarchical level _above_ the business function. It's a nightmare. Trying to pull out the useful business functionality that's interleaved everywhere makes it very hard to pull codebases apart to where different teams can work on them. With respect to Joe's comment here: > Bad: It's very difficult to decide which module to put an individual function in. Break encapsulation (see later) As much as I like Joe's thought process, that "difficult" part is otherwise known as "the real work". All systems which scale in complexity--as opposed to the simple problem scaled in performance--need strong boundaries. They also all have a hierarchical component to them.