What I noticed is that I can take one item (or pile or items) for each point I have in pickpocket. The only ones that ever seem to have anything are merchants though. Although I did get a bunch of arrows off the citidel guards.
I have not used it for awhile though. So it may have changed with the last patch. I have so much gold now that I have not even bothered to loot the battlefield dungeons for the last few (except the rare third level spawn). I just run through and kill everything.
