Indictments sent to Digital Music News by prosecutors working for the Department of Justice reportedly reveal that 90 percent of Megaupload's users were never really uploading. Although it claimed to have 180 million members, the DOJ said the file-sharing giant had closer to "66.6 million registered users as of Jan. 19, 2012." That means roughly 5.86 million accounts ever bothered to upload one file, which the DOJ said verifies its claim that most Megaupload users were simply downloading copyrighted material.
Furthermore, the documents point out that the other 10 percent of users were almost exclusively uploading content. If that is the case, then it's likely the number of accounts both uploading and downloading files was very low. If you head over to DMN, you'll see a more pointed look by prosecutors at Megaupload users they found particularly noteworthy.