Is there any way to track the history of items in ArcGIS Online? Specifically, I am looking for information on changes to item sharing.
There does not appear to be a way of doing this but it's a great idea.
In the ArcGIS Ideas site, this one popped up:
ArcGIS Online Administrator Tracking
But, it's not exactly what you are looking for (though, it's in the right direction).
Maybe it would be a good idea to make new idea.
There is a way to do this currently through the REST API. The documentation for the History API can be found in the Early Adopters Community for ArcGIS Online, which includes samples of how to tell sharing changes on items. You need to be an Administrator of the organization in order to access this log for items that you don't own.
Here is a blog about the program:
Announcing the ArcGIS Online User and Item History Log Early Adopters Community!
Retrieving data ...