Keeping beneficiary designations up to date is important as Jason Zweig points out in his article, When Your 401(k) Has a Bad Heir Day.
He cites the example of three adult children of a wealthy telemarketing executive who died suddenly. His Will states that all of his assets are to go to his children. Most of his assets were in a 401(k) account which named his wife, married only two months earlier, as the beneficiary of the account.
The executive should have asked his wife to sign a waiver and then name his children as the beneficiaries of the 401(k). It is important to remember that a beneficiary designation overrides the provisions of a Will.
Consult your estate planning attorney for further information.