Ok, maybe I am missing something here but doesn't a electronic fence work on both sides, so his dogs will get zapped too. Right?
Depends on how you have the wire fence installed. If you have an outer fence that is electrified and the inner fence is not then the dogs on the inner fence will not get the shock. I see no reason to electrify a fence though. I do know that if I had 6 acres of property I would not want my dog or dogs to be able to have access to all 6 acres. I'd like to be able to supervise them and the area for people coming on to the property and trying to steal the dogs. One or two acres is plenty of space.
One of our local dog parks is 2 acres and there is room for plenty of dogs and there owners. I have seen at least 30 dogs in the all dog area which is only 1.5 acres and the under 35 pound area is 1/2 acre and there is plenty of room. So a full acre or two fenced in would be way more than enough space for two or three dogs.