If you're having issues with activation, please contact [email protected] directly. As a number of users reporting this are seeing it on the Windows 8 beta, please also note if that is your case that beta operating systems may be unsupported.
I am thinking to buy this game but I will not do it if it has always online DRM. I play mostly singleplayer so I could agree for online activation and Steam (since it has offline mode, but that's all I'm willing to accept).
Activation is only required on install/first run. Steam must be running (as the game uses Steamworks features), but may be in offline mode.