What is the difference between services.arcgis.com and services.arcgisonline.com

Discussion created by dcaldwell-esristaff on Apr 16, 2013
I've written code that will load a service from services.arcgisonline.com into arc map as a map service layer, but it doesn't seem to work on any service from services.arcgis.com. It crashes when it tries to enumerate through the server objects.