I've been following them to Travincal and Eldrich and stealing their drops before going hostile. They pick up fast so you've got to be right on top of them. So far today I've gotten a Duriel's shell, Stormrider, 5mfsc, 20 life/6 fire res sc, and a bunch or rares worth 35k. They don't seem to pick up magic items, including charms and jewelry, so you don't have to jump on those right away.
I noticed that if I TP from Travincal, and they are making another trip there, they get confused at the portals and just stand or run back and forth switching from concentration to vigor. Throwing up a TP in another act seems to straighten them out, though one time funsad was pacing back and forth for several minutes before giving up and quitting the game.