Generally, this concept is important whenever we present new information to people. It must be close enough to a known world in order to help people use their experience from such another world in the new environment. This applies to VirtualReality, for example. It must be close enough to the RealWorld. People must be able to make predictions, plan ahead. If not, the experience deteriorates quickly. The "other world" must not necessarily be the RealWorld, however. From one world to the next, simple changes are possible. And as time goes on, these new worlds are "acceptable" to base new worlds on. Just don't stray too far. User Interfaces, for example, should not be too strange or too new. Introduce simple changes at a time.