Please excuse the crudity of this model. I didn't have time to build it to scale or paint it.
This is a rough mockup for the T100217 task on one way we might want to visually represent the information.
This is the top 100 extensions by download count (see P661 for raw data). Data covers Dec 25, 2014 - May 19, 2015. Stats are from ExtensionDistributor statistics ONLY.
The extensions in blue are those that are not running on WMF-related projects. ergo third-party MediaWiki installations.