The Tax Relief Act of 2010 has brought some notable changes to estate tax law. While the increase in the lifetime gift tax exemption to 5 million may leave many with a sigh of relief feeling that they may not need to get to creative since their estate is below this threshold, this Smartmoney.com article points out that for those who have formula clauses in their existing estate planning documents, this change may have the unintendedeffect of disinheriting your spouse.