I think there is a good case for bad UI*. In fact, if you are a text content provider, I believe bad UI might be your greatest asset. However, Let me define what I think good UI is first, or at least how its often perceived. I'll define good UI – or perfect UI – as the simplest way to find and ingest information or execute a predetermined task, in the briefest period of time. It’s a basic definition; good UI is easy and fast. So to invert this, bad UI would be hard and slow, though not broken.
I think bad UI can prove especially useful and even delightful in certain circumstances. But in order to talk about that, we need to talk about the perfect UI: Search.