ARG's potential legal issues

In tutorial I asked Keven about some of the legal ramifications of ARGs when the players may over step some boundaries. As Kevin said often players go far outside what is expected and intended by the puppet master. This got me thinking as to liability for ARG's.
Aside from obvious cases where groups such as 4chan illegally target someone as a "game" the other instance came to mind of what if a player did what they THOUGHT the puppet master wanted, only to wind up in some sort of legal mess (trespass or hacking something they shouldn't have). Obviously the puppet master had no intent, and therefore cannot be held responsible, but what if the player thought they were able to go over the area in question, or access that email or web page because they thought it was part of the game? I can see a potential worry for players, puppet masters and for the companies that bankroll them, more for publicity stakes, than from a legal point of view if a bunch of their players got arrested or fines.