Yep, a few do the heavy lifting. A good portion of the paper analyzes the crowd/participants as a whole and touches on what effects they may have on each other (I think), but I wasn't able to understand it well enough to have any thoughts.

As for the muscle-powered, on page 4 of the document there's a graphic that shows the ratios, and it's no contest. The vast majority are involved in announcing (the situation) and uploading / re-uploading (the information). Informing and spreading.

It's obvious to me in hindsight, but I wasn't expecting such a wide gulf.