It is country dependent. Might sound odd but Steam does actually check what country your in based on your IP adress, from there it looks up what content should and shouldn't be available to you. The games that are banned in your country won't show up on the steam store.
Just bought the game myself through steam. Would welcome a trainer so I don't have to use the give all weapons cheat for ammo, but whatever works is cool.
[Edited by tommygunner70, 2/23/2012 12:38:25 PM]