Your users have lots of extensions installed, are they all being used? GAT Shield has a partial answer to that question.
Google provides no API to measure extension activation. However, some extensions can open web pages when in use.
We can track this use through the browsing.
Many extensions are represented by a code. With GAT you can map this code to a meaningful name so that is how it appears in reports.
You can also tag these pages as ‘Extensions’ for easy filtering and reporting.
Once a tag is applied, you can filter for this app in the Browsing Explorer with the tag marked ‘Extension’ to see only extension use and the time extensions were used and number of start events for extensions.