I think since the last google maps update this has been a problem... I can't tell since I'm a new droid owner, but I remember my first day 3 weeks ago, my maps was looking right at my location like scarily... a few days later I think there was an update and after that my location has been like 20 yards off forever now.
compared to my friend who uses an unlocked iphone, my maps are pathetic.
My street view has been off by roughly a block I'd say 80% of the time since getting my Droid in December. Navigation, for whatever reason, is usually a good deal more accurate, although is still off a bit from time to time and has given me the wrong directions (basically telling me to make a right when it should have been a left or vice versa) a handful of times... interestingly, those mistakes have all been so close to my destination that I've been able to circle back and find it.
people in my area have been dealing with everything being centered in Gainesville, Florida (5 hours away), navigation, gps, even weather channel. I know ESPN and CBS thought the world revolved around Tim Tebow and the Florida Gaytors, but I didn't know the weather channel did?!?!?\
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I look for the GPS switchover to Denver anytime now
If you're that far off it's probably not using GPS and is falling back on another, less accurate, method of locating you. There are a lot of threads that covers steps you can take to get GPS working again.