Circuit breakers (and fuses) are worthless for surges. Before they pop, they let through way to much juice. Pop! goes the circuit behind them. On the other hand a good surge supressor clamps down alot faster, but instead of interupting the current spike it shunts it off in a different direction. A common method is to shunt the spike to ground, and hold the difference between the line the spike comes in on and ground to a reasonable voltage difference. Note: in a surge condition a spike can and will raise the ground's voltage significantly, however the circuit is spared because the voltage between it's ground and the line with the spike are held within reason. Problems do arise when you have many different devices interconnected, each with its' own ground. If a surge comes in and the circuitry can't get all the devices to agree on a ground, then devices may be dammaged where the grounds don't match. To get around this one tries to place all linked devices on the same electrical circuit. Failing that, one then goes to isolation circuits.