It has to depend upon the circumstances, to say that any dog that bites a human will do it again and should therefore be put down is blinkered and shortsighted and shows very little knowledge of dogs.
If you step on a dogs foot, or its tail for instance, and you are a stranger to that animal there is a more than strong chance it will react strongly and possibly unpredictably.
It may well snap at you, but even if it does, in almost all cases the bite it might give you won't be a savage mauling.
All dogs have a bite reflex and most bites trigger this reflex.
The bite isn't a full power one, it's a warning one, the odds are it won't even break the skin.
If you get bitten by a dog that has not learned the bite reflex it'll have you down to the bone, even a little jack russell.
My dad had a golden retriever, she was as soft mouthed a dog as you could ever meet and would greet everyone by grabbing their hand in her mouth and 'walk' them into the house.
Technichally you could well call this a bite and if you ripped your hand out of her mouth you'd probably hurt yourself.
Their are some that would now bleat, "I want some compo! that dog bit me and I want it put down."
I know who I'd rather see put down

A dog sees some little fingers waggling through the letterbox, wrong though it is it sees them as something to play with, or letters as something to tear apart.
It doesn't make the dog a viscious beast, quite apart from which, as any postman will tell you - and as I said earlier - if your hand goes through the letterbox technically you are breaking and entering.
Therre are even rules about the how and the where of how postmen are supposed to deliver letters and gain access to your property.
If a dog is injured, or has come back from the vets after an operation, if disturbed or frightened it is likely to bite.
If a dog is blind or deaf and is surprised it is likely to do the same thing.
It is not a black and white issue, not all bites are because of some viscious, unpredictable and dangerous dog.
My own dog will have your hand off if you put your hand though a part open window in the summer when he is in the van, ditto if you were a thief and tried to nick my van while he is in there, but I sure as hell wouldn't have him put down if he bit someone in this context.
time is getting on!
Work beckons!!
Ian