Everyone brought up some really good points on the 22 but one that was not brought up was the price of guns and ammo. I have a CZ 452 in 22 lr I paid about 200 bucks for, try to buy a decent centerfire for that price, it will, with boring regularity, shoot .5" groups at 50 yards. There is no recoil, no muzzle blast and ammo is dirt cheap I can shoot all I want, which makes me a better shot and hunter, and not worry about disturbing people a half a mile away.
A bit more about the effectiveness of the 22lr, I sat on the end of a dirt runway in AZ and with the rifle I described above, shooting from shooting sticks, with a 10X mil dot scope, killed 3 Jack rabbits in 7 shots, at a leica lased 211 yds. This isn't a tall tale, I did it. Chris