Vertical farming, the best solution to support an ever growing population or just a scam?
IMHO it has a lot of potential but not being able to grow grains really is something that should be tackled sooner rather than later. But I could see this being used by self sustaining communities to provide lots of food while using very little space. And it's technically more environmentally friendly than just using vast stretches of land to produce the same amount of food.
I think space efficiency is not really a big factor. As others have said, every tower casts a shadow, so the sunlight is not being used.
However, it is good for indoor planting, because under a roof, space efficiency is necessary. So, we could have some sort of climate controlled greenhouses, and they would surround a vertical farm. The greenhouse "shadow" would be outside, and it means your plants are safely indoors, protected from heat and cold.