I got JOSM, grabbed my local area including a GPS track from someone. The GPS track conveniently goes out on a peninsula and "stays within the lines" of the underlying coastline; the road map doesn't.

davidearl, I'm obviously a newbie and don't see a button to correct this - can you point me to it? :)

Oh, I forgot, in "view" the underlying grey terrain/blue ocean is also misaligned with the street map.

Thanks for the comments!

I'm using Potlatch, not JOSM (I suppose I should get JOSM now), and the misalignment is between the overlaid street map and the underlying displayed Yahoo satellite imagery.

I did, however, overstate the misalignment by a bit; I checked using gmap-pedometer and the straight-line misalignment of my home address is only about 445 meters, not 500. Still, an entirely different neighborhood of town, and of course we're coastal so some other neighborhoods show up as being in the ocean... ;)