by dont-waste-time
In short, megaupload requires HTTP Post to send the request. Those file download links we usually see can be got by HTTP Get. For HTTP Get, all information can be got from the url. HTTP Post has some information in the HTTP request body, not in the url. On the server side, the server can do anything to deal with the Post request, for example, send you a file that is only accessible locally in attament to you. That is basically what happens for megaupload.