Luke - this is actually a very good thread and an important topic for all GT fishermen.
I'd always encourage people to be cautious and look behind them when they get into a casting position. If there is any doubt, don't cast. The other point is if you are on a boat with a cowboy, pull them up firmly a soon as it happens. Believe me, this is not a time to be shy because they are not putting themselves in danger, just everyone else on the boat. It is your trip they are going to spoil, not theirs.
I've generally had little problem because I pulll people up immediately but I have heard of some cowboys who friends have fished with who will cast directly over other people in the boat if they think there are fish in that direction.
There are some really exciteable people out there who don't seem to pay any heed to safety.