A lot of bad things can happen when a person is blamed for something they did not do. The most obvious one is that an innocent person may be punished. That is not a good thing. No one likes to be punished, but it is especially bad when the punishment is undeserved. Besides that, a perfectly happy person that gets blamed for something they did not do gets bitter. Even if the event does not merit punishment, the innocent person feels like they have been wrongly persecuted, and that is enough to ruin anyone's cheerful disposition. Not to mention that wrongly blaming someone can ruin a friendship. If my best friend blamed something bad on me, it is likely that I would be pretty upset at him until he apologized or until I got really bored. If he thought I was responsible for some bad happening, it is also quite possible that he would be upset with me, and over something I had not even done. Luckily such a situation has not occurred, so I will end this line of thought before I jinx it.
Another bad consequence of wrongly blaming someone is that the wrongly blamed someone may carry a bit of a grudge. For instance, a merely hypothetical example, when your little sister draws on the wall with crayon and blames you. You see, that is the kind of blame that sticks with a person, even though you little sister was only around three at the time. By purely hypothetical, I really meant actual example that really happened and that I still have not forgotten. But I do see how you could get the two confused.
So, as you see, blaming the wrong people is bad. Especially when you only blame one person, because that is just not fair. Thus you should blame everyone equally for everything bad that happens. Just kidding. That would be bad too. instead, you should refrain from blaming people until you are absolutely sure they have done what ever it is that is in question.