I've noticed that, not only in mapquest, but also in multiple vehicles' nav systems that the street where I live has about 1/3 mile inacccuracy from house number to actual location.
my address: 2320 Fairview Drive
Alton, IL 62002

donfricke@hotmail.com

Since NavTech is the main data provider to MapPoint, I assume that MapPoint uses the same technique as NT in geocoding addresses. That is that a link knows its street name and the start and end numbers of the street. The position for a number between the start and end numbers are intrerpolated between these, resulting in an inexact but memory efficiant solution.

- Niklas

I think in that case Microsoft may be using GDT as the data provider for the area in Alton. Navtech generally drives the roads and the GPS accuracy is perfect.

Eric