Ever since we got wind that Battlefield 3 wouldn't be released on Steam, we've heard multiple rumours that folks were working behind the scenes to make it happen. This is another of those rumours, backed with a smidgeon of evidence.
The first piece of evidence is this competition, found on the Sapphire Select Club website. One of the prizes in this competition is "[o]ne (1) PC Game code for Battlefield 3, redeemable for the game on Steam".
Now this could simply be a mistake on the part of those running the competition. In fact, Sapphire are probably so used to writing competition Ts and Cs that reference Steam codes that they just assumed it would be the same with this comp.
But there's also this. One user found that the PBSetup.exe file, which is used to install Punk Buster for Battlefield Installs, has been updated with the following install files...
C:\Program Files (x86)\Electronic Arts\Battlefield 3\ C:\Program Files (x86)\Steam\SteamApps\common\battlefield 3\ C:\Program Files\Steam\SteamApps\common\battlefield 3\ C:\Program Files\Electronic Arts\Battlefield 3\
Despite this accumulating evidence, it could be difficult since Battlefield 3 is built into the Origin and Battlelog system -- but ultimately the audience available on Steam is just too overwhelmingly large to ignore. We believe it'll only be a matter of time before we see Battlefield 3 on Steam.