Yeah, if someone said "Give me $20 and a sandwich or we'll detonate this nuke in Paris", and you knew the threat was serious and had very little chance of catching the person, I don't know if it's time to negotiate then, but I still don't think so. I can see the reasoning behind never negotiating with terrorists.

If someone is crazy enough to be willing to detonate a nuclear bomb in the middle of a city, could you trust that that person wouldn't explode it anyways if he got his money or whatever he was after? You're placing your trust in the hands of the bad guy. I don't think that's ever wise.