Just out today is the court's decision in United States v. Quality Stores, Inc. The issue was whether severance payments constituted taxable wages subject to FICA. The Court's analysis is – how can I put this politely? – a bit dense, so let's cut to the finish:
The severance payments here were made to employees terminated against their will, were varied based on job seniority and time served, and were not linked to the receipt of state unemployment benefits. Under FICA's broad definition, these severance payments constitute taxable wages.
You can link to the slip opinion through the Supreme Court's web site.
Once again, the government gets its money. What more is there to say?