There is a hole in Windows 8 activation process that allows pirates to get a free license of Windows 8 using the Windows Media Center (WMC) upgrade promotion which will last until January 31, 2013.
As you know Microsoft has closed the hole with volume keys and every copy of Windows 8 needs a unique key so pirates would have to rely on KMS activation, that needs to be "refreshed" every 180 days. Microsoft is giving away free WMC upgrade keys to Windows 8 Pro users but their system don't bother to check if the Windows 8 key you are currently using is valid. Since the Windows Media Center key comes directly from Microsoft and is unique for each user, it activates Windows 8 Pro.
So pirates are now installing Windows 8 Pro using any valid key, even if it's in use and, once the system is installed, they are activating it with a KMS server that takes all keys as valid. And using the free WMC upgrade key to activate their copies of Windows 8.
I don't want to encourage piracy so I'm not posting about the KMS activation here. Microsoft hasn't patched the hole which allows you to upgrade to Windows 8 Pro from pirated Windows 7 copies. Some people calls it Microsoft's strategic decision to encourage pirates to use genuine Windows but I'm pretty sure this newly discovered hole will be patched soon, hopefully.