Lightning Rod Hack By Using Satellite Dish
Lighting is a lot of energy dumped in a small amount of time. The grounding wire used (most likely from the existing power network) is most likely not rated to handle that kind of surge.

Proper lighting rods and their grounding wires are very generous in their current carrying capacity to minimize the energy absorbed due to internal resistance and heavy enough to make sure there is enough thermal mass to stay cool enough to not melt the wire and/or set fire to your house.