The losses to predators are less than you would expect when using the electric fencing. I'm only about 15 minutes from Salatin, and we do definitely have our share of predators here: hawks, foxes, coyotes, black bear, raccoon, skunk, opossum, and bobcats in addition to the domestic dog. Yet, the losses he sustains are within an acceptable limit which still allows him to make a profit with his layers and meat birds. I imagine that pastured poultry has different problems than poultry kept on the same land continuously. Perhaps what he loses to predators is made up for by not losing birds to some of the common diseases.
If you are interested in how electric fencing helps to prevent predator losses, you could read this article by another Virginian, Harvey Ussery: http://www.themodernhomestead.us/article/Electronet-1.html. From what I understand, the electric fencing not only acts as an initial deterrent, but the animals in the area actually learn to avoid the fencing over time, and there are fewer and fewer incursions. I'm not sure all of that is in Ussery's article, but he explains how that worked for him in his book.
I agree with the others that his methods are certainly unlikely to work for everyone. Nothing ever does, right? But his eggs are delicious - part of the reason why I started keeping chickens - and his meat and eggs are served in many of the restaurants around here. His business model is working for him. I wouldn't say it's snake oil. Perhaps it's more like rice or soymilk: many people find it fussy and laughable, but others are simply allergic to anything else.