Yeah, dragonchild mentioned the (valid and true) employer side of the story, that the employer is assuming a lot of risk when they make a big hire. But the other side of the coin is that the potential hire is as well. A bad fit is terrible for both parties.
I expect potential employers to be happy to discuss all aspects of the position with me, and I try to be as up front as possible when I'm interviewing a potential employee. The cost of making a bad hire is just too great not to do otherwise.