Read this article.
http://www.alternet.org/story/146686/wh ... d_problems
It is a pretty interesting article. It proves why vertical farming will not be able to replace traditional agricultural methods. First of all, vertical farming will rely heavily on electricity-generated lighting rather than sunlight. But to provide that much electricity-generated lighting will require us to dramatically scale up our electricity production by many times. It is unfeasible to increase our electricity production multiple times just to provide the lighting necessary for large-scale vertical farms. We don't have enough energy to dramatically increase our electricity production to support large-scale vertical farms. There are plenty of other issues with vertical farming, which the article discusses.
I think this article is worth reading, because it shows why the myth that technology will always solve humanity's problems. Vertical farming is the new hype that many cornucopians use to justify their belief of infinite population growth being possible on a finite planet. This article shows why large scale vertical farming is not feasible, and will not avert a population crash/die off in a post peak oil world.