It's not a bad idea to reflect and think about the effects one's images may have on people. But to what extent are we responsible?
I would agree that each person is in charge of their own decisions, but should we at least take responsibility for influencing someone, either directly or indirectly? Interesting questions to ponder.
I'm honestly more concerned about the influence we have on other photographers, not the subjects. It's the photographers who may suggest the couple pose on a railroad track, or otherwise risky situation, and the couple is trusting that photographer. But if the photographer hasn't done their due diligence, and is simply trying to recreate an image they saw somewhere, there could be serious consequences.