While postal delivery areas data is probably used for sending out mailers to a specific neighborhood to target specific demographic groups and prospect for customers. I love when my mailbox is full of recyclables, Not! Bing Maps Spatial Data Service actually has quite a bit of data included and here are some samples of how they can be viewed up on a Bing Maps Web control "Virtual Earth" map.

		Load Multiple Boundaries GeoData This code sample shows how to request the boundaries for 5 zip codes and render them on the map.
		GeoData Choropleth Map This sample shows how to create a simple choropleth map which retrieves boundary data from the GeoData API in the Bing Spatial Data Services.
		GeoData Search Boundary If the search location has an entity type value that is supported by the GeoData API, a boundary will be requested and if available, displayed on the map.