[Inziladun]

I don't know if this has been mentioned, but Boromir was the sharer of a secret on which the fate of Middle-earth hung. It was far more sensible for him to set out with the Fellowship than to be allowed to risk the long journey back to Minas Tirith alone. I'm not saying he would have deliberately let anything slip if captured, but Saruman particularly could have engineered that event, and then all bets were off.