A friend of mine just sent this photo showing how he picked up a Dr. Mercy-type rifle from a random loot drop in the Southern Shelf. I noticed that the bottom right corner shows "Backpack 98/33"... how is he carrying so many items ?
EDIT: I should mention that he's on a PS3. He and I play single-player, as he doesn't have an internet connection at home. We communicate by email on his phone, so his messages are terse and sometimes cryptic. When I asked him how he did this, he said something about maxing out his inventory and then trading somehow with a second character that he brought up with another controller. I still don't get it. I've only ever had an additional inventory slot when I received a mission reward and already had a full backpack. Guess maybe I should actually call and talk to him... :-)