1. The price of electricity would rise long before we reached 100GW, thus no problem. Price always solves the problem.

2. That article assumes the genre and capital cost of the mining equipment is irrelevant. Thus with cpu-only mining, this problem will be much improved, as the both the home electricity cost per KWH and the cost of the equipment per Watt consumed are higher than for Bitcoin's specialized ASIC mining. For example, Butterfly lab's shipping 10GH/s consumes 50W and costs $349. The Intel i7 costs $329 and consumes 87W, but to build an entire system costs about double that. Also Intel has just begun focusing on power consumption reduction so this will improve at a faster rate than ASICs will.