I donīt see how it could, LOGICALLY SPEAKING, backfire. Kiraīs power basically works as a prison for the boy. He has to live on as if everything was normal. The moment he tells somebody or so much as hints about Kira, that person is blown to death and time is rewinded, reminding the boy once again that he better keep his mouth shut.

Edit: One way to counter this, I imagine, is Jojoīs healing ability. The moment the bomb gets off, he needs to start healing, so that the effects of the explosion are negated the moment they happen. That way he could surive even after being told about Kira.