Yes, a moment of silence is an appropriate way to acknowledge someone's death. It allows everyone a moment to remember that person in their own way. That moment of silence because a way for all doing the remembering to chose how they best remember the individual, without influencing other memories of the person.
I think it is a respectful way to acknowledge someone's death, just light lighting a candle or attending a vigil, it is a traditional and widely accepted way to do so. I think that for those closer to the person, a bit more might need to be done than just a moment of silence.
The moment of silence that honors a memory of another individual after death has been under scrutiny lately. This technique was a way people could draw away from a religious angle and now some are suggesting that even this action is not appropriate. Remembering people who have passed is tough, but this offers a way while being respectful to everyone.
It is not appropriate unless you do not know them. In addition, it depends on the setting and who the person was. Not everyone regards one person's death the same way they do another. I guess it is a nice gesture, but some people make a moment of silence more about a political statement than anything.
I don't think a moment of silence is maybe appropriate is not the right word, but it just does not feel right. One if I die, I don't want people bowing their heads down in a tragic appearance, as if im still dyeing at that moment. I'm already dead, gone, the best thing to do is wish me luck to the gate of heaven, and actually be happy about it. Because I don't have to worry about debt, credit, car payment, house payment, job, and all that stress of living in the Morden word.