ArcDeveloper REST
ArcGIS developers are embracing Web architecture as enthusiastically as we on the open source side. Maybe even a bit more. Via Dave Bouwman, and James Fee.
The community that would become OSGeo has long criticized ESRI and its users for tepid support of WxS protocols and formats. I suspect (cynic, me) that lesser enthusiasm had more to do with business competition than to foresight of the changing tide, but it seems to me that ESRI and the ArcGIS server users, having drunk less of the kool-aid, are now in a better position to innovate with REST than the free and open source GIS community. The Windows tools don't hurt either.