Heres a nice article from Business Week about Service Prototyping (link).
The article shows how prototyping helps understand the holistic experience that a service gives:
Think of GM’s (GM) On-Star in-vehicle security and communications system. A physical model of the blue OnStar call button doesn’t begin to convey the relief a lost or injured driver would feel on hearing the operator’s voice. Marketing departments get this, it’s why an OnStar ad focuses on the customer rather than the button, yet the distinction is too often overlooked in the development process.
Services generally are simple to prototype but can be very costly to implement. This is why in the AT-ONE project we focus upon creating prototypes early in the design process and encourage companies to implement a strategy of continually creating new concept prototypes.
Evidencing is a kind of prototyping that is often even cheaper to produce. The AT-ONE project is focussing upon developing guidelines for evidencing services. Evidencing aims to produce tangible evidence of a service at an early stage. Not the whole thing, but just enough to experience what the service does and how it feels as a user to utilise the service. I will be writing about evidencing later in a seperate blog post.