Don’t underestimate the anti-personnel effectiveness of .22LR.
Some anecdotal evidence:
“In my 20+ year’s as a former LEO I’ve
seen more people killled from a .22 LR Hollow Point;
than I have any other caliber, bar none.”
http://www.youtube.com/watch?v=-DzLQGv-w5M
While I would rather have a 22LR with me over no firearm at all, I would not leave my larger calibers at home to carry it for personal protection.
I have never found anyone that teaches firearm self-defense that would recommend it over .380 and up.
Just because it is common, doesn’t make it a better choice. It is common for the same reason I shoot a 22 more than my other weapons; it is cheap to shoot.
A bad day plinking with the 22 is still better than a good day working.