Diane has a great post.
In perhaps more simple terms, why would a buyer opt to buy a house, at a future date, for a set price, in a declining market? As Diane pointed out, because they cannot do it any other way.
Your problem is that as values continue to decline, the chances are, with all the inventory available in most areas, buyers will either buy, or opt to rent.
I would advise you consult a Realtor that knows three things:
Your home, your market trends, and your personal situation. For most owners that need to move, renting it out is about the only option unless they either arrange a short sale or are willing to take the financial hit.
However, I was in that same situation, and renting it out turned me into an accidental real estate investor.
Get competent advice from professionals that know the situation.