Is it `this` or callbacks tripping me up?

gistfile1.txt

asked to geolocate 570 Renfrew St, Winnipeg, MB 0 index.js:12
asked to geolocate 600 Renfrew St, Winnipeg, MB 1 index.js:16

in callback Address {textAddress: "600 Renfrew St, Winnipeg, MB", foo: 1, latlon: null, mapObj: null, geolocate: function} 
geocode complete [Object]
placing a marker at 600 Renfrew St, Winnipeg, MB hf {k: 49.8609077, D: -97.19679180000003, toString: function, j: function, equals: function…}
in callback Address {textAddress: "600 Renfrew St, Winnipeg, MB", foo: "seen", latlon: hf, mapObj: Mj, geolocate: function}
geocode complete [Object]
placing a marker at 600 Renfrew St, Winnipeg, MB hf {k: 49.8602556, D: -97.19661889999998, toString: function, j: function, equals: function…}

addresses
[Address
foo: 0 latlon: nullmapObj: nulltextAddress: "570 Renfrew St, Winnipeg, MB"__proto__: Address, 
Address foo: "seen" latlon: hfmapObj: MjtextAddress: "600 Renfrew St, Winnipeg, MB"__proto__: Address]

index.js

var geocoder;

function Address(textAddress) {
  this.textAddress = textAddress;
  this.foo = "";
  this.latlon = null;
  this.mapObj = null;
}

Address.prototype.geolocate = function(afterGeo) {
  console.log("asked to geolocate", this.textAddress, this.foo);

  addressObject = this;
  geocoder.geocode( {'address': this.textAddress }, function(results, status) {
    console.log("in callback", addressObject);
    addressObject.foo = "seen";
    if (status == google.maps.GeocoderStatus.OK) {
      console.log("geocode complete", results);
      addressObject.latlon = results[0].geometry.location
      addressObject.mapObj = afterGeo(addressObject);
    } else {
      alert("Geocode was not successful for the following reason: " + status);
    }
  });
}

var a = [ "570 Renfrew St, Winnipeg, MB", "600 Renfrew St, Winnipeg, MB"];
var addresses = [];
for (var i=0; i < a.length; i++) {
  addresses[i] = new Address(a[i]);
  addresses[i].foo = i;
}

function initialize() {
  // map stuff removed
  geocoder = new google.maps.Geocoder();

  for (var i=0; i < addresses.length; i++) {
    addresses[i].geolocate(function(obj) {
      console.log("placing a marker at", obj.textAddress, obj.latlon);
      // This doesn't matter to the example, but it does place the markers in the right spot.
      var marker = new google.maps.Marker({
        map: map,
        position: obj.latlon,
        title: obj.textAddress
      });
      return marker;
    });
  }
}

google.maps.event.addDomListener(window, 'load', initialize);