The ubiquitous MVC (Model-View-Controller). Though simple in its definition, quite a hard concept to grasp and harder still to implement. Many of the frameworks that claim to be MVC do compromise on MVC-ness somewhere or the other. Quite difficult this MVC business.
Let us consider the faceless components (usually libraries), MVC applies to them as well. Here the View part could be the APIs exposed (analogous to the GUI screens that allow human interaction).
Then perhaps, i am kind of forced to think that when each of these parts in split and zoomed further, there is an MVC sitting pretty again. Assuming this fractal nature were true, then no doubt that MVC is harder because fractals are complex indeed.
This blog post that I came across partly reinforced my belief.