Just recently for the upcoming release of ArcGIS Online, the zoom level, or level of display has been set so that users can finally zoom to very detailed levels (1:71!) which is great for features close together on the ground. The basemaps don't currently draw any clearer beyond a certain level, but you can continue to zoom until that level is reached.
However if a local basemap is used (ie not ESRI's) you cannot zoom in beyond the level set when creating it. Does anyone know if / how to set a local or custom basemap to perform the same way in ArcGIS Online - to zoom to the 1:71 level (even if distorted after a certain level) without having to create the cache at that level?