It is hard for me to conceive of a debt between spouses. We marry and share good fortune and bad - so the separation of finances is a foreign thing to me. It makes me wonder if the marriage is on a solid foundation.
Emotionally you would think not, but in many cases people are engaging in second or third marriages. In some cases there a prenuptual agreements due to disparity in net worth of both parites. As a financial planner I have seen too many cases where things went wrong for couples financially. Depending on the state your in and the applicable laws, there can be some benefits to formal agreements in which debt obligations can come into play. Sometimes there are estate planning reasons that it may actually be beneficial.
After being married for eight years, this seems like a really odd question. One spouse will always owe the other something, but in a good relationship, nobody should keep track. When I say "owe", I don't just mean money. You can "owe" time and affection, especially when you have kids.