There was a similiar post a few month back about killing an elephant with a 22 (newbie with no idea of calibers) and then their was the infamous post about a guy in Colo. scaring away a mt. lion with his pellet gun everytime it went after the pets. Both posts eventually became flaming sessions. Truth is you could kill a hog or elephant for that matter with a pointy stick (that's what the natives used for thousands of years), but who would want to? It is right up there with playing russian roulet with an automatic.
Yes I too have had the experience of killing hogs on a farm with a 22 (mine was a contraption that fired a 22 blank which propelled a blunt steel shaft into the head, the steel shaft would then cause massive brain trauma and the animal would die instantly)but this was when pressed against the head when we were prepping them for sausage and they were in pens or shoots and could not run at us. Would I take a 22 to hunt hugs, NO!! The calibers that the origianl post mentioned are plenty enough for hogs. I have used everything from .38 special to 45/70 on then (I always carry a 38 snub nose when hiking and I came across a sow and her piglets one time, she charged I unloaded all the chambers into her and ran!!!! she died after about a 20 yard rush. I would never take .38 hog hunting, but it worked.) I like a nice lever action carbine/guide gun in 30/30 or 45/70 for brush hunting hogs or deer and the follow up shots are as fast as an auto.
Happy hunting and please leave the 22 for rabbits/squirrels and ground hogs (not ferral hogs).