Almost everything you and your wife buy after tying the knot is marital property. There are exceptions, such as stuff bought with money from before your marriage or gifts given to only one of you. A credit card isn't marital property but credit-card debts are. Even if she's the one who racked up the debt, you may end up responsible for some of it after a divorce.
Spousal Credit Cards
Even if the card is in your wife's name, that doesn't mean she's the one who has to pay. If you order a card for her as an authorized user on your account, all the spending on the account is officially in your name. The credit-card bill comes to you and you're the one the company will hold liable if the bills go unpaid. The debts are marital debts, and what she buys with the card is marital property. That's only significant if you get to a divorce court.
Dividing Up Debt
The general guideline is that if a marriage ends, the couple should divide marital property and marital debt fairly. That usually works out as a 50-50 split, but it's not iron-clad. If your wife ran up thousands of dollars as an authorized user, the judge may decide she should pay the bill. The judge may also divide debt unequally because he thinks one of you is more at fault in the marriage.
The credit card company doesn't care about your divorce decree. The divorce agreement can assign your wife full responsibility for any debts she ran up on your account, and other debts as well. That doesn't take your name off the bill: If she violates the divorce decree and doesn't make the payments, the card company will come after you. You may have to go back to court to get another order forcing your wife to repay you.
If you live in a community property state such as Texas or California, a 50-50 split is more than just fairness. Legally, you and your spouse own 50 percent of the marital assets, regardless of who makes the most money or buys the most stuff. You're also responsible for 50 percent of the debt, even if you only contributed 1 percent of the total debt load. Whether your wife ran up the debts on your card or her own account doesn't affect that.