While some cyberlockers use ads, they mostly make money by encouraging people to buy premium accounts. They do that by making the free download process cumbersome, asking users to poke around to find the download button, and then sometimes forcing them to wait for a minute or more before they can punch another button and download the file.
Megaupload shutdown: What the site’s departure means for other traffic-hogging “cyberlockers.” - Slate Magazine
