Guerra Bobo (2013) has questioned whether Lüders conditionalization for quantum probabilities supplies a notion of conditional probability worthy of the name. I agree in large part with Guerra Bobo's critique; indeed, I show how her critique can be sharpened. But while valuable in itself, the main virtue of the critique derives from the fact that it prompts questions about the nature of quantum probabilities that engage some of the more important and contentious issues in the foundations of QM. I show how understanding the role of Lüders conditionalization in quantum probability theory helps to illuminate these issues
