Is there a "best practice" for what the spatial reference should be for Open Spatial Data? Do I use what seems to be the "web" standard of WGS 1984 Web Mercator Auxiliary Sphere (3857) or our local/regional NAD 1983 HARN StatePlane Arizona Central FIPS 0202 Feet Intl? I've gone to some of the other Open Data site on the web and I've seen both. Is there an official opinion/standard?