If you've opened a few power supplies, you may have seen some with darkened areas on the mounting boards. This is when the resins turn to carbon. Carbon is a conductor of electrical current. Thus, it can act as another component in the circuit and change how things regulate. Eventually the change to carbon cascades and causes total failure but any visible heat damage of this type to the boards is a warning of things to come.
It seems bad caps are becoming a problem that is no longer one of a bad manufacturing issue. At one time several yrs. back, the formula for capacitors was stolen in an case of industrial espionage.