.22 is a waste of time and space. If you can shoot a .22, you can learn to shoot a gun in an effective caliber. If you take your safety and the safety of loved ones seriously, learn to shoot an effective caliber, minumum .38/9mm.
All this talk about it being better than nothing- it's not, because it lulls you into a false sense of security. And the joke about "no one wants to get shot with ____ caliber" is ridiculous.
Lets re-phrase the question this way: since most SD scenarios involve an average of 2-3 shots, we'll give it the 3.
A' 6'2" 250 lb ex-con is in the room with your 11 yr old (daughter, granddaughter, whatever) and you get those 3 shots to stop him.
A 90 lb pitt bull has your (daughter, gradndaughter) cornered and is getting ready to lunge at her throat. You have those 3 .22 shots. Still feel like it's enough?
You have to STOP a threat. This isn't TV. No BG is going to see your little .22 gun, and rationally think, "Hmm, I calculate my odds at exiting this scenario as being disadvantageous. I think I shall terminate this endeavor." So that mess about "no one wants to get shot with blah blah" goes right out the window.
Taste the wares, Email.