For information on this, see http://forum.openstreetmap.org/viewtopic.php?id=73869

Homes in this community have a "common" address that is the same as the lot number and stored in the addr:* tags. These are displayed on the exterior of the house and are used by delivery companies, service providers, and others. They also have a "formal" address (assigned years later by the county) that is stored in the addr2:* tags and used for property taxes, real estate sales, and emergency services. For full background, see the post in the OSM forum at http://forum.openstreetmap.org/viewtopic.php?id=73869.