Yes mate ... why don't you put some ads in the page where the downloadable link generating for the free user, for 30 seconds or if you want for 60 or 180 seconds, but I don't prefer the shorten links bc it'll affects the uploaders who already using another shorten links service ( like adf.ly ), it will be too commercial if the downloader has two ads pages for getting each link, the external shortening link, and filemates shorten link )...

That's what I see, although for me I don't care too much because more than 95% of my links now are already for premium users only and I don't use any of shorten link service.