If you have a power, you can dream about what will happen in the future. But, what we need to know is the dream are divided into good and bad. If someone in your dream would die, would you choose to tell him if you got the chance?
Never mess with the design death has for us! Haven't you seen any Final Destination movies? Shit rolls downhill real fast once you mess with the fate of another...
But when you know that your dream will come true, and don't tell them, then you blame yourself, don't you? That is what I think...
Nah because when you intervene you give that person extreme paranoia about their life and they might thank you by never leaving you alone and calling you some kind of god or something. Then you have no choice but to be the prophetic king of the future and be responsible for all things and win the lottery for everyone who is ignorant. More esp more espionage, life of a medium.