Another area where married couples have an advantage is with estate tax issues. (dinesentax.com)
In simpler estate plans where there is no federal estate tax issue, it may just be easier to designate your spouse as a primary beneficiary and perhaps your trust or adult children as a contingent beneficiary. (insuranceandestates.com)
Doug also posted a link to a BDO Dunwoody bulletin on U.S. Estate Tax Issues for Canadians which points out that the estate tax is a double whammy: (canadiancapitalist.com)