Hi Jocelyn,
In your Lead Database, you can create a Smart List that looks like this:
![0EM50000000QhL4.jpg 0EM50000000QhL4.jpg](/t5/image/serverpage/image-id/12462i5B12C6106219B9C0/image-size/large?v=v2&px=999)
And it should pull in anyone who has shared the content. By altering your Default Columns, you can create a fairly details activity report. It's not exactly what you're looking for, but it might be a start!