yep, sock puppeting is where a troll has multiple accounts/names and uses them to back up. Emma Bowyer is a famous case of this.
re troll hunting, I think it depends on the sbject matter. not long ago there was a troll who had "lost" her fiance, needed brain surgery, and had a zillion other problems. it became fairly obvious that she was trolling, and posters were getting sucked in, offering help, PMing addresses/phone numbers and generally supporting the op. a few more seasoned posters tried "subtley" suggesting that people be more careful, then out and out accused her/him of trolling. they got rounded on, which was (imho) unfair.
trolls like this do a great deal of damage and can effect people profoundly (look at Hillllls and the effect it had on some fellow anorexics, and the CVQ palaver - the amount of time and effort that some posters put into helping her, and reliving their own ordeals, and SS nearly lost us some fabulous posters) in these instances its better to call troll (once you are pretty sure) and report. if one poster (cant remember who) hadnt hunted DM and subsequently found pictures, she would probably still be here.
then there are the ones who throw a lit match and watch it burn. they post contentious threads, then sit back and watch the fight. in these cases report and ignore.