Justice thinking

Why is everyone so wound up about Casey Anthony and whether she "should" have been found guilty? The jury said the prosecution failed to prove its case. She may indeed have done the deed, but the burden of proof is on the state, beyond a reasonable doubt. The defense planted a reasonable doubt (cause of death not definitive) so the jury acquitted. Granted, Casey Anthony did some stupid things, but there is no law against stupidity. If there were, we would all be locked up. But then, who would hold the key?