Well, I'm not going to read all seven pages so I hope I'm not repeating anyone. My method works and kills gophers without fail.
Start with Juicy Fruit gum. Buy it in bulk 10 packs at at time. Buy a package of earth worms. The mini crawlers used by fishermen and can be bought at any drugstore or K-mart or Wal-mart. Then get a 1 gallon plastic milk jug. Finally, get some of those disposable nitrile or latex gloves. Automotive stores sell them for mechanics to use in order to keep their hands clean.
Start with the milk jug and clean it out with plain hot water. Now, cut a hole in one side of the milk jug about 3 inches high and along one whole side and about an inch up from the bottom. Don the gloves. You do not want to put your taint on the bait. Put the worms in the jug through the opening you just made. Unwrap 2 packs of gum, 10 sticks altogether. Toss them in with the worms and toss them around a bit. Let the gum set in the jug overnite for best effect. Be sure to store your worms in the fridge and they will last a few weeks and can be used over and over. Go out and expose the hole of a gopher. This isn't as easy as it sounds. On first thought you would think to just dig up the mound. But that mound isn't an access point, it's jammed up with dirt and it isn't easy to find the tunnel this way. Instead, poke around with a steel rod of some sort all around the mound until you feel that you've broke in to a tunnel. excavate the tunnel about 10 inches so you can see down into the tunnel in each direction. Place the gum in the tunnel, about 2 sticks in each one and in each direction. Push it way back or else the gopher will just cover it up when he's shoving dirt into the tunnel opening. The gopher will absolutely eat the gum, especially since it smells stong of worm now. The gum will goo up their innards and they will all be dead within a week. I've killed dozens this way and have now worked my way back out to where I am gopher free for at least 300 feet in any direction from the house. It's cheap and easy. My neighbors spend tons on professional gopher/mole removal and still loose many plants each year to them. I haven't lost a single plant since I starte to use this method. Good luck!!