From a recent report by Social Security's Office of Inspector General (OIG):
In a 2009 audit, we determined SSA issued approximately $40 million in improper payments to more than 6,000 beneficiaries although it had received notification they were deceased. In a 2013 audit, we determined SSA had issued about $31 million in improper payments to 2,475 beneficiaries although it had received notification they were deceased. ...
Since our prior reviews, the number of beneficiaries who continued receiving payments after SSA recorded their death information on the Numident had declined. However, 1,281 beneficiaries, including 56 identified during our prior audits, continued receiving payments for months or years after SSA received notification they were deceased. SSA received death reports for these beneficiaries and recorded dates of death on the Numident. However, SSA did not record the death information on the beneficiaries’ payment records or terminate their benefit payments. System controls designed to prevent continued payments to deceased beneficiaries were not effective in these instances.
Prior audit work has indicated a likelihood that some death entries on the Numident were erroneous, and beneficiaries were actually alive. However, we determined that 678 of the 1,281 beneficiaries had death certificate information or other Numident entries indicating their death information had been proven or verified.
We estimate SSA issued the 678 beneficiaries approximately $20 million in improper payments. Further, we estimate SSA will issue approximately $6 million in additional improper payments over the next 12 months if these discrepancies are not corrected. ...Note that OIG seems a lot more concerned about payments made to dead people than the danger of mistakenly cutting off benefits to living people.