What are the implications of the federal government's obligation to withhold income tax and social security taxes from employees' pay checks?

2 Payroll tax and social security taxes, required by law to be withheld by employers from employee pay checks, 26 U.S.C. 3102(a), 3402(a), are held in trust for the federal government. 26 U.S.C. 7501(a). These "trust fund" taxes may be recovered directly from the officers and employees responsible for the collection of these taxes as "responsible persons" in the event that they are not paid to the government. 26 U.S.C. 6672; Slodov v. United States, 436 U.S. 238, 259, 98 S.Ct. 1778, 1791, 56 L.Ed.2d 251, 264 (1978).