seller information and loan balance

that as long as you explain up front why you want it, it usually isn't a problem. However, I have learned that when they are hesitant to give it to you, you will find that it usually their confrontational style and they can't help themselves. My advice is to politely tell them to call you when they have a change of heart and move to the next property. You can't fix the world; you can only offer solutions to those that want the help.

Make sure this isn't the last question you have to ask them so you can keep moving along. I find that I can get their payoff info when you ask later on "What's the minimum you need for a payoff?" and that usually leads right into how much they have remaining on the mortgage.
If they still won't tell you, that should raise some red flags.
Think about it, why wouldn't you tell somebody that's interested in buying your house how much you have left? What if their offer ends up being lower than what you owe? Following that, they may not be telling you because their house is underwater and would end up being a short sale.
Like Bill says, they could have a confrontational attitude as well, which will only lead to headaches down the road.
Trust your intuition, see if it relates to their story.

Some people may kick tires while others slash 'em.

then you ask them that kind of questions... some people don't like to talk about their finances, for whatever reasons... especially if they see you as a stranger; but if you make them feel at ease and explain that you need to know the numbers for 'the property' (don't say 'how much do you owe on your home'; instead say something like, 'how much would the bank take if you were to sell this property to me').
Listen to what they tell you, repeat it back to them... it will make them know that you are listening to what they are saying...people like that.

I usually get it, but some people don't want to. I guess I should tell them that I would need to know the information in order to factor that into my offer. Seems like that could lead them to still ask for more, but eventually I would see the numbers if we did the papers.