The industry term is "scope creep." The everyday human term is "a bunch of extra junk." Use this master list, and future predictions, to manage what you need and what will bring you value.

One of the first few questions you answer when starting a web project is what are the core features. What's our site going to do for people? The simple answer you start with usually grows into a rambling monster of: instant personal messaging, event auto-recommendations, mobile video chat, holograms and real life status pokes.