Creating Passionate Users has has an eye-catching article on the power of using unexpected context.
One way to delight users is with the guy-in-the-unexpected-context phenomenon. You know the story: you take the same train to work every day. One Saturday afternoon you’re in a cafe when you spot a familiar face at the next table. “Hey, it’s the guy from the train!” you think, with a smile. Then the guy from the train notices you, and his eyes light up. You start a lively conversation moving from weather to espresso to geopolitical forces. You exchange URLs.
The thing is, you took the train with this guy for the last 18 months and never gave him a moment’s thought…until you saw him at the cafe.
That’s the power of unexpected context.