Properly operating motors generate heat, but more often than not they're designed to dissipate the heat. When a fault occurs, a motor can consume more power than it's supposed to, generating heat that can burn out the motor.
Faults can occur for a variety of reasons. The device being driven by the motor may prevent the shaft from rotating, or there may be sufficient drag to significantly slow the rotation. The motor itself may be at fault with broken brushes, shorted coils, or a variety of more esoteric problems. In a worst case scenario, the motor may cause a fire.
Dumb systems may come to the rescue if they employ a circuit breaker, shutting down the system when too much power is consumed. However, the shutdown could happen after the motor experiences damage. Intelligent motor-control systems typically respond more quickly, and may often report problems to a high authority. The former is actually a relatively easy task for sensor-based systems that need to track rotation speed and power consumption as part of their normal motor-control process. Shut down will occur at the first sign of a problem. In fact, fault detection is a key feature of moving to intelligent motor control.