Just the other day I'd written up an article about the wonderful Dark Mod project, which requires the original Doom 3 to play. If you thought to yourself, "Gee, Sean, that sounds mighty swell; I think I'll go pick up a copy of Doom 3 on Steam and give it a try!", well, you can't do that anymore, at least not yet.
You see, Timmy, publisher id Software has restricted the game from sale on Steam, though its store page still exists. Naturally, this is in light of the recent launch of Doom 3 BFG Edition aka Doom 3 Superior Edition. It's understandable id wants to direct people towards its definitive version of the game, but if it's at the expense of the mod community, surely something must be done.
Responding to the matter, id says they're "looking into options", which I'm taking to mean they're debating whether or not it's worth it to confuse semi-casual gamers to bring joy back to modders. Time will tell.