There is no logic behind the damage that lightning can do. In the past 3 years, I've had two instances of "bad" storms here. On the first occasion, we had a cloud-to-cloud strike directly over the house. There was no structural damage, because there was no actual strike to the house, but the voltages induced by the overhead strike in local cabling took out a Sky+HD box (it wouldn't dial out), an ADSL filter, a DECT phone base unit, and an ethernet router.

The second local strike happened about a month ago. The electricity pole outside a property about 400 yards up the road got a direct hit. We live out in the sticks, and our electricity comes off the 11kV "agricultural grid", with a step down transformer outide a neighbouring property, feeding them and us with 230V. When the strike happened, all the power went off for about 20 seconds, and came back on. I didn't see the strike, but I heard the bang, and saw the cloud of smoke around the pole. I immediately thought "this is going to be expensive", but curiously neither I nor my neighbour suffered any damage to electronics equipment.

I'm not sure how much would have been saved in the first instance by using a surge arrestor, because overhead strikes induce high voltages directly into the wiring. The damage to the router occurred to the ethernet side, not the ADSL side. The damage only affected one port of a 4-port router.