It is the AddressesV3 service. We're planning on using it (for the website redesign) to make sure that the addresses are correct (enough). There's a significant number of people who register and quit/get fired, yet still have to make one final filing (for a state government agency) that we snail-mail them a final "I'm done with this" paper form to fill out. And every couple of years an envelope gets returned as "undeliverable".