Once a Snapchat users receives and opens an image or video, they have a maximum of 10 seconds to view it before it disappears and they can not access it again. For brands, this provides a sense of scarcity that posting to other social networks like Facebook or Instagram cannot provide.
For brands who want to offer vouchers or promotions through Snapchat, the app provides a means by which the offer can be limited only to its followers, with no chance of it going viral as it'll disappear shortly after opening. That theory might sound counter-productive at first, but the feeling a consumer gets when they feel part of something small and exclusive is hugely powerful in terms of garnering brand loyalty.
The image above shows a promotion by New York-based 16 Handles, which exemplifies this approach.
2. The unexpectedness and surprise in its messages