There are several situations where you might want to know something but asking outright is dangerously close to being rude, and might even be offensive. One of the classical situations is a job interview, where as a candidate you don't want to be seen as too forward, but you want to have the information.

Some questions in such a situation could be:

• "What happened to the last person who did this job?" - the answer to which could give you an example of how they treat people (he was laid off, he took leave, she gave birth, etc). 

• 
  "Why isn't the company promoting from within?" Listen for the corporate philosophy as well as the boss's reasons. It will give you insight into potential snags in your own upward mobility. If many people are being brought in from the outside, find out why.

• 
  "Who will evaluate my performance?" When? How? This question could be the most important one. For example, if your evaluator won't be working closely with you, you'll need to know how judgments will be made.