On the map page, if you click on the list on the left of the map, you'll see more detail on the member you clicked on, including "Address Confirmed" if that's true.
So obviously if you haven't confirmed your postal address on mtvan, it's well worth doing that, as you're more likely to be chosen for a job.
The way it works is simple, just click on "Confirm Address" in Account, and in a few days you'll receive a postcard in the post at your address, on which there's a PIN to enter to confirm that you live or work there.