Every dead body turning into a zombie worked fine in George Romero's zombie flicks. I personally like that idea better as if you want to be even a tiny bit realistic, if it took bites to turn you, days for you to die and then maybe a day to come back, the zombie plague would be over before it started. If EVERY dead body comes back, then you got some serious doo doo on your hands.
I watched the last episode again today and something else dawned on me. A few episodes ago Rick says they have to start using their knives etc. to kill zombies as they are running low on ammo. Carl shows up and instead of going "Dad, Shane is behind you and gonna chomp your butt" so he can knife him, he decides to go all Rambo and gun shane down. Whats this do? Alert the whole herd thats nearby to come and overrun the farm. Further proof Carl should be put down for the good of the group. :lol
If Carl would of just shot the deer instead of trying to go pet it, he never would of been shot. Otis would still be alive. Sophia would still be alive. Dale would still be alive. The bad guy raiders wouldn't of run into the group so all of them would be alive. Randall would be alive. Shane might not of gone off the deep end as badly as he did and would still be alive.
See? Every death this season can be blamed on Carl. String him up!