Here is a summary of the issue:
Windows 8 PC Battlefield 3 AMD Graphics cards (4xxx, 5xxx, 6xxx series, 7xxx seems ok). Any version of the driver, 12.10, 12.9, 12.8, 12.11 beta 11.
The game will work normally for a random amount of time, perhaps 20 minutes - 30 minutes. After the elapsed time, the game becomes a slideshow, the whole PC becomes incredibly sluggish. Closing the game and restarting the game results in the same issue immediately. Only upon reboot will this issue be resolved. Task manager will show almost all the physical ram in use. There will be much misc hard drive activity as well (presumably writing to the paging file).
Here are a few topics created on this issue on other websites.
http://battlelog.battlefield.com/bf3/forum/threadview/2832654625233545341/1/
http://www.tomshardware.com/forum/840-73-windows-extremely-high-memory-usage
This is definitely a bug, hopefully the PCGaming Wiki community can help out here. I honestly think we need to bring this to the attention of AMD or Dice. My friends are incredibly frustrated with gaming right now, I do not blame them. This issue is so odd.