Google has a new (free) phone service that's interesting. You can set up a new phone number that will forward a call to any number of other phones. So it's like a virtual phone, pointing to physical devices. Here's a quick overview:
I had been thinking of something similar for mailing addresses. If the postal service would recognize a set of virtual addresses, it would be possible to make a free service that would resolve a virtual address to a physical mailing addresses as well. Then if you move from one physical address to another, you could just update a pointer in the abstraction layer rather than notifying hundreds of people about the change. The virtual mailing address could always be the same.