>Defensible and sustainable (pure cost of hosting plus needed attention/maintainance) I understand. Dunno what you mean with unique... But at least the thrashing way of strategy evolution shows that they at least realize the danger - Blackberry and Nokia disappeared almost silently.

'unique' is a shortcut for 'perceived as unique' by the customers, and it covers 2 dimensions:

- an underlying compelling need for the product or service - eg: for consumer follow the fashion, for businesses, make more money either by selling more or spending less.
- the perception that this product or service from this supplier provides a unique value: performance, quality, security or whatever individual value criteria may be