This weekend I upgraded the code in the clustering example to Version 6 of Virtual Earth. This means we now utilise the bulk add shapes method and the bounds for a birdseye scene. Additionally I added some throttling logic for ajax webservices and showed how to provide legacy support for PNG icons in IE6.
Read the article here:
http://www.viawindowslive.com/Articles/VirtualEarth/ClusteringPinsinVirtualEarth6.aspx