Nice thread : ) I had been thinking about these kinds of things more but hadn't had a chance to read through the thread until now. I'll post my thoughts on a few issues here, but there's so much going on that this could really be about five threads.
Regarding my plot cycling question, I think I probably should not have pointed it out. The player cycling the plots was one of the people I was more friendly with at the event, so pointing out the error was mostly an empathetic involuntary response (because I would hate to wait and tell him that he won on an error after the match if it ended up mattering). As a general rule though, I think spectators should not point out errors. Even if it seems like a really obvious error, no one should know what's happening in the game better than the people playing it and it could very well be the case that the spectator is the one overlooking something (eg maybe you see someone defending against Core Set Stannis without a Lord character. What you don't realize is that Stannis' text box was has been blanked until the end of the phase by some other effect. Now not only have you disrupted another match, but you've drawn both players' attention to Stannis' ability which one or both would have been more likely to forget about later when choosing targets for kill effects, deciding which characters to marshal, planning out the challenge phase, etc.).
Regarding scouting, I would prefer if the onus were on the players to ask spectators not to watch, rather than on the players to ask if it were okay to watch, but ultimately I think it's a judgment call and would be okay with whatever the TO decided. When I go to a big tournament, I want to watch the best/most veteran players play and learn some things from them. I think some players' worries about scouting are legitimate though (but in practice it would be pretty difficult to prevent others from getting the jist of your deck even if they were asked to leave after completing their games, at least for tournament settings like at the Cranberry Cafe where matches take place in pretty close confines). I am glad this thread was started because I hadn't realized some players in AGoT cared so much about scouting.
For people who are watching games, I think it is important to remain expressionless and not give anything away to the players (avoiding looking at players' hands as suggested above is a good policy). I also think that spectators should not make comments audible to players. Even innocent comments (eg making a joke about Old Nan turning Maester Aemon into a raven for the Carrion Bird combo) could have an unintended ramifications.
Regarding passive effects, I am with FATMOUSE. If you notice that your opponent is forgetting to resolve a beneficial passive effect and you don't point it out, you're cheating. It's stated very clearly at the end of the FAQ: "Can I ignore a passive ability if I don't like its effect? No. A passive ability must initiate whenever a game occurrence would dictate its initiation." Likewise, you can't ignore passive abilities with negative effects for you and see if your opponent points them out. If the effect uses the word "may" (eg Vigilant), I think it's okay to assume your opponent decided to resolve the ability without choosing any targets/options. Obviously, you don't have to point out when your opponent could trigger responses.
I think intentional draws go against the spirit of good sportsmanship but should be allowed (for the reason LGR mentioned that they are difficult to ban effectively). I don't think there is anything morally wrong about them (if a player wants to win the tournament, it's in his best interest to ensure he makes the elimination round), but they just go against the knightly ideals that characters like Brienne and Dunk aspire for.
. There's definitely been a good discussion on scouting and game interference, though. This actually is a topic on which my opinion could be changed if sufficiently broad and effective argumentation was made for disallowing intentional draws, even aside from the practicality of policing the situation.