Government takes over regulation of an economic activity from the market process.
Government regulation fails to prevent the bad it was intended to prevent.
Ergo, the market is incapable of regulating itself, requiring more government regulation
Addendum: This, of course, can be made more general:
Government assumes responsibility for the economy as a whole (the Fed, fiscal controls, housing policy, etc.)
The economy goes through bouts of inflation and recession, and sometimes both at once.
Ergo, since the market process cannot be relied on for self-generated stability, full employment, etc., more comprehensive government control is required.
from Sheldon Richman