Actually, it should work. Only if the contact is saved with full address though. i never tried it.
Interesting, I've never tried this. I'll have to check it out.
However, I will remark that this isn't all that helpful, or at best, is a pain in the ass. If I have someone in my contact list and have their address on there, I probably already know how to get to their location, though I guess the Mazda system can be useful if I'm going there from a different start-point than usual. But frequently when I'm using a GPS nav system, I'm going to someplace new, and it seems rather cumbersome to have to add a new contact every time I go to some restaurant or whatever, just so I can navigate there. I don't really want all the businesses I've traveled to stored in my contacts list.
Because of all this, and the lack of traffic updates, I've mostly given up on the in-car navigation. It just isn't worth it: with Google Maps, I can search for a restaurant or other business (or just look at the map and pick one of my starred locations), press a button to navigate to it, and go, and if there's a traffic jam it'll re-route me if possible. The OEM system just doesn't have any of that convenience. Sometimes I like to use the OEM system as a back-up, just in case GM gives me some weird directions, as all nav systems seem to do from time to time.