Your hint (the anvil over the head;-) about the Earth's rotation diminishing under such a power generation system is possibly valid, but the quantity of such added transfer may be insignificant.

The real devil would be in the details.

I've always viewed the lightning generation process as a great example of generating electricity from the environment. As the clouds (water) move over the Earth, they generate a charge and pick up some electrons. When the environment these clouds move over facilitates it, these clouds generate huge electrical charges.

Supposedly 100 lightning strikes occur every second all over the world. Each one has an average of 40 kiloamperes, enough to power 100 watt bulb for 60 days.

So 100*60= 240,000 kiloamperes per minute
*60=14,400,000 kiloamperes per hour.
*24=864,000,000 kiloamperes per day.

So in 1 day enough atmospheric electricity is generated which could power 21,600,000 100 watt bulbs for 2 months. If the average home has daily electrical consumption (on average) of fifty 100 watt light bulbs running 24/7 then this daily lightning energy could power a large city of 720,000 homes for two months. In 6 days - a years worth of power for this metropolis.

Yet all this electricity is simply wasted on exploding tree trunks, damaging property and scaring women, children and pilots.

I don't think anyone believes that this electrical generation is slowing down the planet. Water basically act as a huge electron magnet and pulls electrons from the other atmospheric elements. This power generation is more properly collation & redirection of the Earth's existing electrons. A thunderstorm is the byproduct of clouds that have hoovered electrons.

The Van de graff generator is another cool example of this spark created between polar charges when imbalanced and conditions permit it.

The trick is controlling this process on a planetary scale and using electrostatic induction to pull the charge from the magnetosphere into plants that can power all the nations of the world - forever and ever.

I suspect the planet's magnetosphere will be replenished far faster than we could ever convert this energy into electrical power. With the sun bombarding the Earth with radiation and plasma being formed in our magnetosphere, it should be a straightforward affair of developing the towers which could "hoover" this plasma's electrons to effective usage.

Reaching this plasma and spurring the electrostatic induction is the engineering and financial 2000 pound elephant in the corner. But when the engineering and scientific angles have been covered - it's just expenditure and political will to be generated which would allow almost limitless power the planet for the next ten thousand years.

Can't you see it Tom? The ferromagnetic towers in every metropolis, scraping the heavens like obelisks from Kubrick's 2001? The happy children playing in parklands and who have to look up "pollution" and "radioactive waste" on their mega gigawatt computer system. The land of plenty Tom...it's been here all along, just awaiting for people with the appropriate neuron potential to make it happen.

It's like a vision...

;-)