Johannes’ first article “Creating Thematic Maps with Virtual Earth and SQL Server 2008” illustrates the ability to shade different geo-entities by pulling information out of SQL Server 2008 and rendering it over Virtual Earth maps. Once the data is rendered, it is then clickable and searchable by the exposed lat/lons in Virtual Earth via the PixelToLatLong method. You can click (or, better yet, right click) anywhere on the map, convert the pixel to a latitude / longitude, then send it to Microsoft SQL Server 2008 (or some other database) for spatial analysis and return the data to the map for display.
Second article, “Creating Heat Maps with Virtual Earth and SQL Server 2008” illustrates how to take information from SQL Server 2008 (he’s quite the expert) and create a rasterized heat map which can then be geo-annotated (using Map Cruncher or based on the Virtual Earth Tile System documentation) and overlain atop a Virtual Earth-based application. Although there is another layer (and, there can be many layers!) this map is still interactive in that you can overlay vector information or grab lat/lons for spatial analysis.