Imagine this scenario: After 11 years of marriage, you and your spouse call it quits and you move out of the house. After you leave, a letter from your former employer is delivered to the house that your ex now resides in. The envelope is clearly marked: "To be opened by addressee only." Your ex opens it and discovers there's a new procedure in place to access your retirement funds online. After following the procedures, your ex drains the account in four months.

This happened to Michael Foster of Tulsa, Okla. He lost $42,126.38 altogether -- and didn't even find out about it until January of the following year, when he received a tax form from the plan provider reporting a distribution of that amount. Foster sent a letter to his former employer's plan administrator, "claiming potential fraud, as I did not request withdrawal from my plan and I did not authorize any disbursement from this plan," according to court documents.