Perhaps I should've fleshed out my post more. "Getting shot in the head with a .22 usually stops the person. Center mass shots can be very effective as well." I more against the idea that a .22lr is just a scaled up bb gun caliber and that it wont stop someone.
If someone wants to be armed with a .22lr firearm for home defense I would suggest a Ruger 10/22. Extremely light recoil, accurate, cheap to buy, cheap to shoot, and the longer barrel length gives the round a bigger boost allowing for quality expansion on hollow points. Couple this with the ten round magazine it comes with it (not to mention larger aftermarket magazines) could be sufficient for a home defense situation.
22lr is not an ideal self defense cartridge, but If all I owned was a 22 rifle I wouldn't feel under equipped defending my house with a 10/22 or Model 60. ---