The idea of a criminal using any body armor is laughable. It's not unheard of in home invasions, but then again, you have the option of a shotgun for in the home defense.
Heart shots are almost as laughable, but not impossible as a the body armor bit. I forget the exact number, but I read a statistic that most defensive shootings happen within 3 yards. Any caliber is pretty potent at the range.
Show of hands, who carries a knife with them most of the time?
As far as the .22 is concerned, the LR is a bit lacking all around, but can be crammed into an automatic that is minuscule compared to even a .32 (summer carry, anyone?). The .22 WMR is also getting to be popular in defense geared handguns (Kel-Tec PMR, Taurus revolvers, ect.). Double the case size, double the fun.