The default basemaps available for the Silverlight viewer, available through ArcGIS Online, are all tiled caches. Certain domains (i.e. utilities) need to have access to basemap data that allows a deeper "zoom" level than what is otherwise available. Even if the larger geospatial context is unusable, the location and presence of valves, meters, mains, etc. give the utility GIS professional the context s/he needs. Please consider adding either:
This idea has been merged with Zoom beyond basemap in AGOL.
- A good, dynamic basemap service that allows users to zoom to whatever level they need, or
- a tiled basemap service that zooms to about 2 or 3 levels beyond the standard 20 available in the topographic basemap.