Baseline (Widescreen) Solution & Issues
Field of View (FOV) can be adjusted (60 - 90) in game menu OPTIONS >> VIDEO (70 is default).
Note: FOV in SP and COOP portions of Battlefield 3 cannot be changed using the game settings, either through the menu field of setting or console string or with the config edit, it only works in Multiplayer and only after you iron sight once (thanks to pyide for this information).
Thanks to fuc847 for this SP and COOP FOV solution
Download this and unrar it.
Run the app, launch BF3 and select the FOV increase you want (+25 degrees or +35 degress) by pressing respectively hotkeys num 7 or num 9.
Please note that it only works after you've zoomed in once, then zoom back out and it should be wider.